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Dear students, prepare for physics class 10th chapter 3 long questions. These important long questions are carefully added to get you best preparation for your 10th class physics ch. 3 exams.
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Our database contains a total of 0 questions for physics Short Questions. You’ll prepare using this huge databank.

Question: 1
Define simple microscope and also derive the formula of magnifying power?
Answer: 1
1-58

Simple Microscope:

A magnifying glass is a convex lens which is used to produce magnified images of small objects.Hence it is also called simple microscope.

Objects position:

The objects is place nearer to the lens then the principal focus such that an upright, virtual and magnified images is seen clearly 25cm from the normal eye.

Magnifying power:

It is the ratio of angular size of final image producd by magnifying glass to the angular size of object seen without magnifying glass.

Formula:

M= Q/Q

Where Q is angular size of final image produced by magnifying glass and Q is angular size of object seen without magnifying glass.

Explanation:

Let Q is the angle substended at the eye by the object when it is placed at the near distance from eye.Let Q is the angle substanded by the final image at the eye when the object is placed close to the eye at a distance less then F.The angular magnification M is

M= Q/Q

Nature:

It produced virtual image which is an larged and upright with respect to the object.

Question: 2
<div>A ray of light from air is incident on a liquid surface at an angle of incidence 35* calculate the angle of refraction if the refractive index of the liquid is 1.25 also calculate the critical angle between the liquid air inter-face?</div><div><br></div>
Answer: 2
2-58

Given Data:

<I =30°

N== 1.52

<r =?

Solution:

Sin<I =0

Sin <r =

1.52in<r = sin 30°

Sin <r = sin30°/1.52

Sin<r =0.33

<r =sin-1(0.33)

<r =19.3° Ans:

Question: 3
<div>Draw ray diagram the show the formation of image in the human eye?</div><div><br></div><div><br></div>
Answer: 3
3-58

Given Data:

F =6cm

M=3

P= ?

Solution:

M =-q/P

3p = - q

Q = -3p

According to lens formula:

I/f = I/p +I/q

I/f = I/p + I/( -3P)

I/f = I/p + I/3P

I/f = 3-1/3p

I/6 = 2/3p

3p =12

P =4cm

Question: 4
<div>A convex lens of a focal length 6cm is the be used to form a virtual image three times the size of the object where must lens be placed?</div><div><br></div>
Answer: 4
4-58

Human eye:

Eye is a organ used for vision.

Image formula:

The parts of human eye which play an important role in the image formation are described below.

Retina:

Human eye acts like a camera, in place of the film, the ratina records the picture.The eye has refracting system containing a converging lens.The lens forms an image on the ratina.Ratina is the light sensitive layer at the back of the eye.

Lens:

In the camera the distance of lens from film is adjusted for proper focus but in eye the lens change focal length. The lens of eye is flexible and accomdates object over a wide range of distance.

Cornea:

Light enters the eye through a transparent membrane called the cornea.

Iris:

The iris is the color portion of the eye and controls the amount of light reaching ratina.The iris also controls the size of pupil.

Pupil:

Iris has an opening at its center called pupil.

Question: 5
What is meant by total internal reflection?
Answer: 5
5-58

Total internal reflection:

When the value of angle of incidence becomes greater then the critical angle, then ray does not enter into the second medium,but reflects back in the same medium such reflection of light is called total internal reflection.

Conditions of total internal reflection:

The ray of light should travel from denser medium to rarer medium.The angle of incidence should be greater then the critical angle.

Explanation:

When a ray of light passes from danser medium, the refracted ray bends away from normal and the angle of refraction is greater then angle of incidence.If we increase the angle of incidence ,the angle of refraction,also increase till at a particular value of angle of incidence,the corresponding angle of refraction becomes 90° and refraction ray becomes paralled to the surface.The angle of incidence that causes the refracted ray in the rare medium to bend through 90° is called critical angle.

Question: 6
An object and its image in concave mirror an of the same height yet inverted,when in object 20cm from the mirror.what is the focal length of the mirror?
Answer: 6
6-58

Given data:

Object distance =p=20cm

Image distance =q=20cm

Focal length = f=?

Solution:

According to the mirror formula:

I/f = I/p +I/q

By multiplying pqf on both sides

Pqf/f = pqf/p+pqf/q

Pq=qf+pf

Pq =f (q+p)

Pq/p+q= f

20*20/20+20 =f

400/40 = f

10 =f

F = 10cm

Question: 7
<p class="MsoNormal"><b>What is uses endoscope write its type?<o:p></o:p></b></p>
Answer: 7
7-58

Endoscope is used for viewing and photographing of the internal structure of human body by using light pipes

Types: Grastroscope Bronchoscope Cystoscope

Question: 8
<p class="MsoNormal"><b>Define concave mirror ?<o:p></o:p></b></p>
Answer: 8
8-58

The mirror whose inner curved surface is reflecting is called concave mirror.

Question: 9
<p class="MsoNormal"><b>What is radius of curvature?<o:p></o:p></b></p>
Answer: 9
9-58

Radius of curvature is the radius of the sphere of which spherical mirror is a part.

Question: 10
<p class="MsoNormal"><b>Distinguish between real and virtual image?<o:p></o:p></b></p>
Answer: 10
10-58

Real image:

The image that can be obtained on screen is called real image rays of light actually converge to form image, image is inverted


Question: 11
<p class="MsoNormal">Define focal length ?</p>
Answer: 11
11-58

The distance between principal focus and pole of the mirror is call focal length it is denoted by f.

Question: 12
<p class="MsoNormal">What do you mean by near point and for point?</p>
Answer: 12
12-58

The near point of an eye is the minimum distance of an objects from the eye at which is produce a sharp image on the retina.

Far point:

The far point of the eye is the maximum distance of a distant objects from the eye on which the fully relaxed eye can focus.

Question: 13
<p class="MsoNormal">Define power of lens?</p>
Answer: 13
13-58

Power of lens is defined as the reciprocal of its focal length in meters.

Power of lens = P = I /focal length on meters .

Question: 14
<p class="MsoNormal">Write two uses of spherical mirror?</p>
Answer: 14
14-58

Now a days America and other developed countries use gaint concave mirrors in their huge telescope, the dentists use concave mirror to observe large image of the teeth of the patients.

Question: 15
<p class="MsoNormal">What is the relation between focal length of a spherical mirror?</p>
Answer: 15
15-58

The focal length of a spherical mirror is one half of the radius of curvature i.e f= r/2 however the focal length of a convex mirror is taken as negative it is because the rays appear to come from the focal point behind the mirror.

Question: 16
<p class="MsoNormal">How you see a printed page of book and why you see some printed words a black areas?</p>
Answer: 16
16-58

We see a page of a book because light reflects from each part of the page in all direction so that some of the light rays from each part of the page enter our eye because almost no light is reflected by the printed words , so we see them as black areas.

Question: 17
<p class="MsoNormal">Define optics also explain the geometrical optics?</p>
Answer: 17
17-58

Optics:

The study of light behavior is called optics.

Geometrical optics:

The branch of optics that focuses on the creation of image is called geometrical optics .

Question: 18
<p class="MsoNormal">What is compound microscope? What should be distance between objects and eye piece of compound microscope?</p>
Answer: 18
18-58

Compound microscope is used to investigative the structure very small objects ,objects lens has smaller focal length then the eyepiece distance between the objective lens and the eye piece is greater then fo+fe.

Question: 19
<p class="MsoNormal">What is radius of curvature and radius of curvature ?</p>
Answer: 19
19-58

A spherical mirror is a part of a sphere the center of this sphere is called center of curvature.

Radius of curvature:

Radius of curvature is the radius of the sphere of which spherical mirror is a part.

Question: 20
<p class="MsoNormal">Define small law and write its formula?</p>
Answer: 20
20-58

The ratio of the sine of the angle of incidence ‘’I’’ to the sine of the angle of refraction ‘’r’’ is always equal to a constant i.e,

Sini/sinr = constant

Where the ratio sini/sinr is equal to the refractive index of the second medium with respect to the first medium.

Sini/sinr=n

Question: 21
<p class="MsoNormal">What is difference between regular and irregular reflection?</p>
Answer: 21
21-58

A smooth surface of silver reflect rays of light in one direction only the reflection by this smooth surface is called regular , reflection the rough surfaces of these objects reflect the rays of light in many directions such a type of reflection is called irregular reflection.

Question: 22
<p class="MsoNormal">What should be angle of incidence for total internal reflection?</p>
Answer: 22
22-58

The angle of incidence must be greater than critical angle in order to get total internal reflection.

Question: 23
<p class="MsoNormal">Define principal focus?</p>
Answer: 23
23-58

Principal focus is a point on the principal axis of lens where a bean of light parallel to the principal axis converges to or diverges after refraction from the lens.

Question: 24
<p class="MsoNormal">Write any two uses of lens ?</p>
Answer: 24
24-58

Lenses of many different types are used in optical devices such as cameras, eye glasses etc, they also enable millions of people to use clearly and read comfortably.

Question: 25
<p class="MsoNormal">Define power of lens give its mathematical form and si units?</p>
Answer: 25
25-58

Power of lens is defined as the reciprocal of its focal length in meters.

Power of lens = p = I / focal length in meters

The S.I unit of power of lens is ‘’Dioptre’’ denoted by a symbol D. If f is expressed in meters so that 1D = 1m-1.

Question: 26
<p class="MsoNormal">What is meant by critical angle?</p>
Answer: 26
26-58

The angle of incidence that causes the refracted ray in the rare medium to bend through 90° is called critical angle.

Question: 27
<p class="MsoNormal">Illustrate the image formation in a convex lens with the help of ray diagram when the object is placed beyond 2f?</p>
Answer: 27
27-58

When object is placed at 2F from converging lens the image is shown in figure below.

Question: 28
<p class="MsoNormal">Why an optician’s tasting room is small , he uses a mirror to help him test the eye sight of</p> <p class="MsoNormal">His patients explain why?</p>
Answer: 28
28-58

If the opticians room is small then for testing the patient’s eye sight original words are placed at the back side of patient and mirror is placed in front of the patient , so that image of words is formed at the distance doubled then the size of room.

State law of refraction:

There are two laws of refraction:

First law of refraction:

The incident ray, the refracted ray and the normal at the point of incidence all lie in the some plane.

2nd law of refraction:

The ratio of the sin of the angle o incidence I to the in of the angle of refraction r is always equal to a constant i.e

Sini/sinr= constant= n

Question: 29
<p class="MsoNormal">Write down total internal reflection?</p>
Answer: 29
29-58

When the value of angle of incidence becomes greater than the critical angle , then the ray does not enter in to the second medium but reflects back in the same medium such reflection of light is called total internal reflection.

Question: 30
What is meant by reflection of light? State and explain laws of reflection?
Answer: 30
30-58
Reflection of light:
We see objects if light from it enters our eyes. Some objects such as the Sun, electric lamps and candles make their own light. We call these luminous sources. Most things that we see do not make their own light but reflect it from a luminous source they are non-luminous objects for example this page, teaching board and the Moon.
Reflection of light is same as for other types waves, such as reflection of water waves in ripple tank. Most object reflect a certain portion of the light falling on them, mirrors reflect more light and in a regular manner. An ordinary mirror is made by depositing a thin layer of silver on one side of a piece of glass and protecting it with paint. The silver at the back of the glass - acts as the reflecting surface.
Suppose that a ray of light is incident on a flat, shiny surface, The following terms are used in describing the reflection of light
1- Incident ray: The approaching ray of light
2 Reflected ray: The ray of light reflected from a reflecting surface.
3 Point f incidence: The point at which the incident ray strikes tha reflecting surface
4 Normal: The line drawn at right angles to the reflecting surface at the point of incidence.
5 Angle of incidence (0): The angle between the incident ray and the normal.
6 Angle of reflection(0) : The angle between the reflected ray and the normal
Question: 31
<span style="font-size: 10.5pt; line-height: 107%; font-family: Arial, sans-serif;">What is meant by reflection of light? State and explain laws of reflection?</span>
Answer: 31
31-58

Reflection of light:

We see objects if light from it enters our eyes. Some objects such as the Sun, electric lamps and candles make their own light. We call these luminous sources. Most things that we see do not make their own light but reflect it from a luminous source they are non-luminous objects for example this page, teaching board and the Moon.

Reflection of light is same as for other types waves, such as reflection of water waves in ripple tank. Most object reflect a certain portion of the light falling on them, mirrors reflect more light and in a regular manner. An ordinary mirror is made by depositing a thin layer of silver on oner side of a piece of glass and protecting it with paint. The silver at the back of the glass - acts as the reflecting surface.

Suppose that a ray of light is incident on a flat, shiny surface, The following terms are used in describing the reflection of light

1- Incident ray: The approaching ray of light

2 Reflected ray: The ray of light reflected from a reflecting surface.

3 Point f incidence: The point at which the incident ray strikes the reflecting surface

4 Normal: The line drawn at right angles to the reflecting surface at the point of incidence.

5 Angle of incidence (0): The angle between the incident ray and the normal.

6 Angle of reflection(0) : The angle between the reflected ray and the normal

Question: 32
<span style="font-size:11.0pt;line-height:107%; font-family:&quot;Calibri&quot;,sans-serif;mso-ascii-theme-font:minor-latin;mso-fareast-font-family: Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-theme-font:minor-latin; mso-bidi-font-family:&quot;Times New Roman&quot;;mso-bidi-theme-font:minor-bidi; mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA">Derive spherical mirror formula.</span>
Answer: 32
32-58

To determine the magnification of the image, and its position with precision, it is necessary to draw very accurate scaled diagrams. The mirror equation on the other hand is a precise mathematical relationship between the object distance and the image distance for a given mirror. The following quantities are included in mirror formula:

F = the focal length of the mirror

Ho = the height of the object

H1 = the height of the image

Do = the distance of the object form the mirror

D1 = the distance of the image from the mirror

M = the magnification of the image

To obtain this relation, we use the ray in normal to the mirror. As a result, the ray reflects at an angle below the principal axis that is equal to its incident angleabove the axis. Therefore, the two green triangles in this diagram are similar, form which it follows that ratios of equivalent sides of similar triangles are equal.

Ho/-hi=do/di eq (1)

The image height is negative because it is inverted. Its is clear that the two yellow triangles in this diagram are also similar, since they are both right triangles and share the common angle ϕ. Thus , by using the same rule of similar triangles we get.

Ho/-hi=do-f/f eq (2)

Comparing equation no (1) and eq (2) we get do/di = do- f/f

To isolate `f’ , cross multiply do f= di (do – f) eq (3)

Divide both sides of equation 3 by do di f, we get do f/di do f = di do/di do f – di f / di do f

Or 1/di=1/f-1/do hence it is know as mirror formula. It relates the distances of the object and the image to a concave mirror , in terms of the mirror, in terms of the mirror’s focal length. The ratio of the height of the image to the height of the object is define as the magnification, M;

M =hi/ho =di/do

We derived the magnification and mirror equations for a concave mirror forming a real image, but the equations apply as well to convex mirrors and to virtual images if we use the sign conventions described below.

Question: 33
<span style="font-size:11.0pt;line-height:107%; font-family:&quot;Calibri&quot;,sans-serif;mso-ascii-theme-font:minor-latin;mso-fareast-font-family: &quot;Times New Roman&quot;;mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font: minor-latin;mso-bidi-font-family:&quot;Times New Roman&quot;;mso-bidi-theme-font:minor-bidi; mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA">What is meant by refraction of light? What is the index of refraction?</span>
Answer: 33
33-58

Light travels in straight lines in a transparent material, such as air, if it passes into a different material, such as water, it changes direction at the boundary of the two material i.e it is bent.

Refraction of light is the change of direction of light as it moves from one material (called medium) to another.

Refraction of light is same as for other types such as refraction of water waves, in ripple tank.

The following terms are used describing the refraction of light

1. Incident ray:

The ray of light approaching the boundary ( refracting surface ) between two media.

2. Refracted ray:

The ray of light moving away from he boundary between the two media.

3. Point incidence:

The point at which the incident ray strikes the refracting surface

4. Normal:

The line drawn at right angles to the refracting surface at the point of incidence .

5. Angle of incidence ():

The angle between the incident ray and the normal

6. Angle of refraction ():

The angel of refraction ’ is the angle between the refracted ray and the normal.

7. Optically denser medium :

Medium having a greater refraction effect (slower speed of light); the actual density may or may not be greater.
Question: 34
<span style="font-size:11.0pt;line-height:107%; font-family:&quot;Calibri&quot;,sans-serif;mso-ascii-theme-font:minor-latin;mso-fareast-font-family: &quot;Times New Roman&quot;;mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font: minor-latin;mso-bidi-font-family:&quot;Times New Roman&quot;;mso-bidi-theme-font:minor-bidi; mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA">What is total internal reflection? How we calculate the critical angle for total internal reflection? What are the conditions for the total internal reflection?</span>
Answer: 34
34-58

The angle of refraction is larger than the angle of incidence when light passes into a medium of a lower index of refraction, This leads to an interesting phenomenon. As the angle of incidence increases, the angle of refraction also increases.

At a certain angle of incidence known as the critical angle, the refracted light ray lies along the boundary of the two media. When light strikes a transparent boundary, even though much of the light is transparent boundary, even though much of the light is transmitted some is reflected. Total internal reflection occurs when light traveling form a region of a higher index of refraction strikes the boundary at an angle greater than all light reflects back into the region of the higher index of refraction.

To construct an equation for the critical angle of any boundary, you can use

Snell’s Law and substitute 1 = c and 2=90°.

N1 sinc = n2 sin90°

Since sin90° = 1

Therefore n1 sinc= n2

Hence sinc= n2/n 1

Thus we can define critical angle as ` the sine of the critical angle is equal to the index of refraction of the refraction of the refracting medium divided by the index of refraction of the incident medium

NO transmitted ray

The two condition s required for total internal reflection to occur are as follows.

The light must travel from an optically more dense medium into an optically less dense medium

The angle of incidence must exceed the critical angle, associated with the material.
Question: 35
<span style="font-size:11.0pt;line-height:107%; font-family:&quot;Calibri&quot;,sans-serif;mso-ascii-theme-font:minor-latin;mso-fareast-font-family: &quot;Times New Roman&quot;;mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font: minor-latin;mso-bidi-font-family:&quot;Times New Roman&quot;;mso-bidi-theme-font:minor-bidi; mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA">What is optical fibers? Give some applications of optical fibers.</span>
Answer: 35
35-58

Optical fibers: light can be trapped by total internal reflection inside a bent glass rod and `piped’ along a curved path called optical fiber.

Various glasses and plastics can be used to make optical fibers, Optical fiber transmits a beam of light by means of total internal reflection. Total internal reflection can occur in any transparent medium that has a higher index of refraction than the surrounding medium.

An optical fiber cable has a cylindrical shape and consists of three concentric sections: the core, the cladding and the jacket.

The core is the innermost section and consists of one or more very thin strands, made of glass or plastic. Each strand is surrounded by its own cladding, a glass or plastic coating that has optical properties different form the core

The boundary between the core and cladding acts as a reflector to confine light that would otherwise escape the core . The outermost layer, surrounding one or a bundle of cladded fibers, is the jacket. The jacket is made of plastic and other material layered to protect against moisture abrasion, crushing and other environmental dangers, the light traveling through the transparent fiber always hits the internal boundary of the optical fiber at an angle greater than the critical angle, so all of the light is transmitted through the boundary. Thus the light maintains its intensity over the distance of the fiber.
Question: 36
<p class="MsoNormal">Describe power of lens and it resolving power. What are its units?<o:p></o:p></p>
Answer: 36
36-58

Power of lens:

The degree of convergence or divergence of light rays falling on lens is called power of lens. Instrument makers often quote the power of a lens rather than its focal length. The power of a lens D, in diopters, a dimensionless number, is given by the equation

D = 1/f

Where f is the focal length of the lens expressed in meters. Eyeglass lenses are typically characterized in terms of diopters. The power of a lens in diopters should not be confused with the familiar concept of power in watts. It is an unfortunate fact that the word “power” is used for two completely different concepts. If you examine a prescription for eyeglasses, you will note lens powers given in diopters.

If you examine the label on a motor, you will note energy consumption rate given as a power in watts.

Question: 37
Write a note on reflections of light, law of reflection and its types?
Answer: 37
37-58
Reflection of light; when light traveling in a certain medium falls on the surface of another medium, a part of it turns back in the same medium. This is called reflection of light.
Question: 38
Write a note on spherical mirror; also explain its terms and types.
Answer: 38
38-58
Spherical mirrors; a mirror whose polished reflecting surface is a part of hollow sphere of glass or plastic is called a spherical mirror. In a spherical mirror, one of the two curved surfaces is coated with a thin layer of silver followed by a coating of red lead oxide paint. Thus, one side of the spherical mirror is opaque and the other side is a highly polished reflecting surface. Depending upon the nature of reflecting surface, there are two types of spherical mirrors.Concave mirror: a spherical mirror whose inner curved surface is reflecting is called concave mirror. In concave mirror the size of image depends on the position of the object. Note: both virtual and real images can be formed by concave mirror.Convex mirror: a spherical mirror whose outer curved surface is reflecting is called convex mirror. In convex mirror the size of the image is always smaller than the object.Note; only virtual and erect image is formed by a convex mirror.
Question: 39
how light is reflecting from spherical mirror? explain
Answer: 39
39-58
Reflection of light by spherical mirrors: like plane surfaces spherical surfaces also reflect light following the two laws of reflection as stated for plane surfaces. Light is reflected by the spherical surfaces of concave and convex mirrors according to the law of reflection .Activity: take a convex mirror or a well polished spoon ( using the outside ot he spoon, with the convex surface bulging outward0 and hold it in one hand. Hold a pencil with its tip in the upright position in the other hand try to look at its image in the mirror.
Question: 40
How we can find image location by spherical mirror formula?
Answer: 40
40-58
Mirror formula: mirror formula is the relationship between object distance 'p" , image distance "q' from the mirror and focal length "f" of the mirror.Formula: we can write mirror formula as ;1/f= 1/p+1/qthis equation is true for both concave and convex mirrors.
Question: 41
Explain the reflection of light, its laws and also explain refractive index, how we find the refractive index of medium from speed of light?
Answer: 41
41-58
Refraction of light: Definition: the process bending of light as it passes from one transparent medium into another is called refraction.Explanation: a ray of light IO travelling from air falls on surface of glass block. At the air glass interface the ray light IO changes direction and bends towards normal and travels along path OR inside glass block. The ray IO and OR is incident ray and refracted ray respectively.
Question: 42
Explain the reflection of light, its laws and also explain refractive index, how we find the refractive index of medium from speed of light
Answer: 42
42-58
Refraction of light: Definition: the process bending of light as it passes from one transparent medium into another is called refraction.Explanation: a ray of light IO travelling from air falls on surface of glass block. At the air glass interface the ray light IO changes direction and bends towards normal and travels along path OR inside glass block. The ray IO and OR is incident ray and refracted ray respectively.
Question: 43
What is meant by total internal reflection, explain it? define critical angle?
Answer: 43
43-58
Total internal reflection: when a ray of light enter from a denser to a rare medium the angle of incident become larger from the critical angel no refraction occurs. The entire is reflected back into the denser medium. This is known as total internal reflection.Mechanism of total internal reflection; when a light ray enters from one medium to other medium it bend's toward or away from the normal. Thus , if a light ray enter from denser medium to rare medium it bends away from normal.If the angel of incidence increases the angle of refraction also increase. For a particular angle of incidence the angle of refraction become 90o . When the angle of incidence becomes larger that critical angel no refraction occurs. The entire light is reflected back into the denser medium. This is known as total internal reflection.
Question: 44
What is the use of totally reflecting prism, explain it.
Answer: 44
44-58
A right-angled prism can be used as totally internal reflecting prism.Consider: a right angles prims whose one oft the angles is 90o and other two angles are 45o. When a light ray strike a face of prism without deviation and strikes the face of prism perpendicular, it enter the prism without deviation and strikes the hypotenuse at an angle of 45o. Since the angle of incidence 45o greater than critical angle of the glass which is 42o, the light is totally reflected by the prism through an angle of 90o.
Question: 45
What is optical fiber? how it works? give its advantage?
Answer: 45
45-58
Optical fiber: fiber optics work on the principle of total internal reflection.Structure; fiber optic consists of hair size threads of glass or plastic through which light can be travelled.Core; the inner part of the optical fiber is called core. It carries the light . ITs refraction index is 1.53.Cladding: the outer concentric shell of the optical fiber is called cladding . Its refractive index is 1.39.
Question: 46
What is light pipe, give its importance, also define Endoscope and describe its types.
Answer: 46
46-58
Light pipe; a light pipe is bundle of thousands of optical fibers bounded together. They are useed to illuminate in the inaccessible places by the doctors and engineers.Importance; doctors view inside the human body. it can be used to transmit images from one place to another.
Question: 47
What is prism, write a note on refraction through prism?
Answer: 47
47-58
Prism: prism is a transparent body made of optical glass with at least two polished plane faces inclined towards each other from which light is refracted.Incase of triangular prism: in case of triangle prism, the emergent ray is not parallel to the incident ray. It is deviated by the prism from its original path. The incident ray PE makes an angle of incidence i at point E and is refracted towards the normal N as EF.
Question: 48
Define lenses, explain its types and terms.
Answer: 48
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Lenses: a lens is any transparent material having tow surfaces of which at least one is curved. lenses refract light in such a way that an image of the object is formed.Uses: lenses of may different types are used in optical devices such as camera as eye glasses, microscopes , telescopes and projectors. They are enable millions of peoples to use to see clearly and read comfortably.
Question: 49
Describe refraction through lenses with the help of ray diagrams, also explain image formation when object is placed at different positions.
Answer: 49
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Refraction through lenses; in mirrors images are formed through reflection , but lenses form images through refraction. This can be explained with the help of ray diagram as follow:Ray diagraom of lenses: image foramtion in convex lenses can be explained with the help of three principal rays.The ray parallel to the principal axis passes through the focal point after refraction by the lens.The ray passing the optical center passes straight through the lens and passes undeviated.The ray passing through the focal point becomes parallel to the principal axis after refraction by the lens.
Question: 50
Explain lens formula? what are sign conservations for lens?
Answer: 50
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Image location by lens equation;Lens formula; the relationship between the object and image distance from the lens in terms of the focal lenght of the lens is called as lens formula.Formula: 1/f= 1/p+1/q
Question: 51
Write note on application of lenses.
Answer: 51
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Application of lenses: now we discuss application of lenses in some optical devices such as camera, slide projector and photograph enlarger.Camera: a simple camera consists of a light-proof box with a converging lens in front and a light sensitive plate or film at the back. The lens focuses images to be photographed onto the film. In simple lens camera, the distance between lens and film is fixed which is equal to the focal length of lens. In camera, object is placed beyond 2f. A real inverted and diminished image is formed in this way as shown in figure.
Question: 52
Wire a note on simple microscope.
Answer: 52
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Simple microscope: a magnifying glass is a convex lens which is used to produce magnified image of small objects. Hence , it is also called simple microscope. The object is placed near to the lens than the principal focus such that an upright, virtual and magnified image is seen clearly at 25cm from normal eye.Magnifying power definition: the angular magnification is the relation between the angular size of final image produced bye the magnifying glass and by an angular size of the object seen without magnifying glass.M=angular size of final image produce by magnifying glass/angular size of object seen without magnifying glass
Question: 53
Write a note on compound microscope?
Answer: 53
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Compound microscope: compound microscope has two converging lenses, the objective and the eyepiece and is used to investigate structure of small objects.Features:It gives greater magnification than a single lens.The objective lens has a short focal length fo<1cmThe eye piece has a focal length , fe of a few centimeters
Question: 54
Write note on telescope, also explain structure and principle
Answer: 54
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Telescope: it is an optical instrument which is used to observe distant objects using lenses or mirrors.Refracting telescope: a telescope that uses two converging lenses is called refracting telescope. In refracting telescope, an objective lens and eyepiece are used.Objective lens: form a real image, of the distant object.Eye piece: form a virtual image, that is viewed by the eye.
Question: 55
Write a note on production of electric charges?
Answer: 55
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Production of electric charges: if we rub a plastic comb through our hairs and bring it near small pieces of paper, the comb attracts them similarly, amber when rubbed with silk attracts the small pieces of paper. This property of attraction or repulsion between substances is due to the electric charges they acquire during rubbing.We can produce electric charge by rubbing a neutral body with another neutral body. Following activities show that we can produce two types of electric charge through the process of rubbing.Activity: take a plastic rod. Rub it with fur and suspend it horizontally by a silk thread. Now take another plastic rob and rubit with fur and bring near the suspended rod. Wewill observe that both the rods will repel each other. It means during the rubbing both the rods were charged.
Question: 56
What do you mean by defects of vision . Explain myopia and hypermetropia?
Answer: 56
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Hypermetropia: it is the inability of the eye to form distant images of nearby objects on its retina is known as hypermetropia.Reason; when a farsighted eye tries to focus on a book hold closer than the near point it shortens its focal length as much as it can. However even at its shortest, the focal length is longer than it should be therefore, the light ray from the book would form a sharp image behind the retina.Correction: this defect can be corrected by using converging lens.Explanation: the lens refracts the light rays and they converge to form an image on retina.To observe these rays appears to come from near point to form a sharp virtual image on retina
Question: 57
Write a note on function of human eye?
Answer: 57
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Function of eye: human eye acts like a camera. In place of film, the retina records the picture. The lens form images on retina.Mechanism of eye: the eye has a refracting system containing a converging lens . In camera distance of lens from film is adjusted for proper focus but in eye , the lens changes focal length.Retina: the lens forms image on retina which is a light sensitive layer at the back of eye.Cornea: light enters the eye through a transparent membrane are called cornea.Iris: the iris is the colored portion of eye and control amount of light reaching the retina.Pupil: iris has an opening at its center called pupil the iris controls the size of pupil.Contraction of iris: in bright light , iris contracts the size of pupil while in dim light pupil is enlarged. The lens of eye is flexible and accommodated objects over a wide range of distances.Near point: the near point of the eye is the minimum distance of an object from the eye at which it produces a sharp image on the retina. This distance is also called least distance of distinct vision. Its value for normal eye is 25cm.Far point: the far point of the eye is the maximum distance of object from the eye on which the fully relaxed eye can focus. A person with normal eyesight can see object very far away such as planets and stars, thus has far point located at infinity. Majority of people not have "normal eye".
Question: 58
What is accommodation, explain it
Answer: 58
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Accommodation: variation of focal length of eye lens to form a sharp image on retina is called accommodation. The camera focuses the image of an object at a given distance form it by moving the lens towards or away from the film.Adjusting mechanism: the eye has different adjusting mechanism for focusing the image of an object on retina. Its ciliary muscles control the curvature and thus focal length of lens, and allow objects at various distances to be seen.Object far away from eye: if an object is far away from eye, the deviation of light through the lens must be less. To do this the ciliary muscles relax and decrease the curvature of lens. There by increasing the focal length. The rays are thus focuses onto retina producing a sharp image of distant object.Object close to eye: if an object is close to eye, the ciliary muscles increase curvature of lens, thereby shortening focal length. The divergent rays from nearer object are thus bent more so as to come to focus on retina.Defects in accommodation: the variation of focal length of eye is called accommodation. It is large in young people, while it goes on decreasing with age. Defects in accommodation may be corrected by using different types of lens in eyeglasses.