 # Light Class 10 test paper (With Solutions)

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a.Fill in the blanks
c. One Marks Questions
d. Three Marks Questions
e. Five Marks Questions
f. Case Study Questions

## Fill in the blanks

1. Image formed by a plane mirror is always ______ and ________.
2. A spherical mirror, whose reflecting surface is curved inwards, that is,faces towards the centre of the sphere, is called a ______.
3. The focal length of a spherical mirror is equal to _________ its radius of curvature.
4. Speed of light is _______.
5. Light rays always travels in _________.

1. Erect and Virtual
2. Concave miror
3. Half
4. $3 \times 10^8$ m/s
5. Straight line

### Short Answer Based questions for Refraction(1 Marks)

1. What is refraction of light?
2. What the speed of light in glass is as compared to speed of light in vacuum. ?
3. What is the unit of refractive index?
4. Why a concave lens is called diverging lens?
5. Define Snell’s law of Refraction.
6. Write the relation between the angle of incidence and angle of refraction for a medium.
7. For total internal reflection to occur, the light must pass from denser to rarer medium. Is this True or false?
8. What type of lens is used in a simple microscope?

## One marks questions

1. State the laws of reflection of light.
2. A concave mirror produces three times magnified (enlarged) real image of an object placed at 10 cm in front of it. Where is the image located?
3. The magnification produced by a plane mirror is +1. What does this mean?
4. An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image.
5. Define the principal focus of a concave mirror.
1.The angle of incidence is equal to the angle of reflection, and
The incident ray, the reflected ray and the normal to the mirror at the point of incidence all lie in the same plane.

2. Here m =-3 ( As the image will be inverted )
Now $m= - \frac {v}{u}$
u=-10 cm
Therefore
$-3 = -\frac {v}{-10}$
or v= -30 cm

3. Image of same size is obtained in plane mirror and it is always virtual
4.
Here u =-10 cm, f=15 cm
Using Mirror Formula
$\frac {1}{f} = \frac {1}{u} + \frac {1}{v}$
v= 6 cm

Now $m= - \frac {v}{u} = .6$
So image is erect, diminished and virtual

## Three marks questions

1. Draw ray diagrams showing the image formation by a convex mirror when an object is placed at infinity
2. Under what condition in an arrangement of two plane mirrors, incident ray and reflected ray will always be parallel to each other, whatever may be angle of incidence. Show the same with the help of diagram.
3. A 10 mm long awl pin is placed vertically in front of a concave mirror. A 5 mm long image of the awl pin is formed at 30 cm in front of the mirror. Find the focal length of this mirror.
4. Name the type of mirror used in the following situations.
(b) Side/rear-view mirror of a vehicle.
(c) Solar furnace.
5. A convex mirror used for rear-view on an automobile has a radius of curvature of 3.00 m. If a bus is located at 5.00 m from this mirror, find the position, nature and size of the image.
Answer 2 .When the mirrors are kept at right angles to each other, the incident ray and the reflected rays are parallel to each other. 3. Here v= -30 cm ,$h_i= -5 mm$ (as real and inverted image is formed by Concave mirror) ,$h_o=10 mm$
Now
$- \frac {v }{ u} = \frac { h_i}{h_o}$
$-\frac {-30}{u} = \frac {-5}{10}$
u = - 60 cm
Using Mirror Formula
$\frac {1}{f} = \frac {1}{u} + \frac {1}{v}$
f = - 20 cm

4.
a. Concave mirror
b. Convex mirror
c. Concave mirror

5.
R=3m or f=R/2=1.5m
u= -5 m, v=?
Using Mirror Formula
$\frac {1}{f} = \frac {1}{u} + \frac {1}{v}$
$\frac {1}{1.5}=\frac {1}{-5}+ \frac {1}{v}$
v= 1.15m
The image is virtual seen at the back of mirror
$m=\frac {h_i}{h_o}=- \frac {v}{u} = - \frac {1.15}{-5}=0.23$
Image is erect and diminished in size by a factor of 0.23

### Five marks questions

1. Draw ray diagrams showing the image formation by a concave mirror when an object is placed
(a) between pole and focus of the mirror
(b) between focus and center of curvature of the mirror
(c) at center of curvature of the mirror
(d) at infinity
2. Size of image of an object by a mirror having a focal length of 20 cm is observed to be reduced to 1/ 3rd of its size. At what distance the object has been placed from the mirror? What is the nature of the image and the mirror?

CASE 1: Concave Mirror
$m=- \frac {1}{3}$
f= -20 cm
$m= - \frac {1}{3}=- \frac {v}{u}$
or
v= u/3
Using Mirror Formula
$\frac {1}{f} = \frac {1}{u} + \frac {1}{v}$
-1/20 = 3/u + 1/ u= 4/u
u = -80 cm.

So Image will be Real and Inverted

CASE 2:Convex Mirror
$m= \frac {1}{3}$
f=+20 cm
$m= \frac {1}{3}=- \frac {v}{u}$
or
v= -u/3
Using Mirror Formula
$\frac {1}{f} = \frac {1}{u} + \frac {1}{v}$
or u= -40 cm.
So Image will be Virtual and erect

b>Question 1
What is meant by ‘total internal reflection’? State two essential conditions for total internal reflection to take place. With the help of a ray diagram, illustrate an application of total internal reflection.
Question 2
A concave lens of focal length 15 cm forms an image of 10 cm from the lens.
a) How far is object from the lens?
b) What is the nature of the image?

Question 3
What do you mean by power of the lens? What is the power of a concave lens of focal length 10cm?
Question 4
You are given three medium X, Y, Z .The refractive index of the three medium are n1 , n2 and n3.
It is given that n1 > n3 > n2

1. In which of these does the light travel fastest?
2. In which of these does the light travel lowest?
3. Arrange the medium in ascending order of their optical density?

Question(5 Marks)
A lens X has following observation
1. When the objects is placed at infinity, the image is formed at focus of the lens
2. When a object is placed at 60 cm from the lens, A real image is forced at 10 cm from lens on other side
3. The lens has positive Power
Answer following based on the data given above
1. The lens is
1. Convex
2. Concave
2. The focal length of the lens is
1. 20 cm
2. 10 cm
3. 25 cm
4. None of these
3. The power of the lens
1. 10 D
2. 5 D
3. 4 D
4. None of these
4. When the object is placed at a distance twice the focal length in front of lens, what will be characteristics of the image formed
1. A real inverted image of same size will be formed at a distance twice the focal length
2. A real ,erect image of high diminished size will be formed at a distance twice the focal length
3. A high enlarged image at infinity will be formed
4. None of these
5. When the lens is placed close to the page of book, the letters of the page appear
1. Highly diminished
2. Enlarged
3. Same size as object
4. None of these

## Summary

This Class 10 Light test paper Solved is prepared keeping in mind the latest syllabus of CBSE . This has been designed in a way to improve the academic performance of the students. If you find mistakes , please do provide the feedback on the mail. 