# Light Reflection and Refraction Worksheet

In this page we have Light Reflection and Refraction Class 10 Worksheet . Hope you like them and do not forget to like , social shar and comment at the end of the page.
a. One Marks Questions
c. Fill in the blanks
d. Crossword Puzzle

## Very Short Answer type (1 mark each)

Question 1.
Define the principal focus of a concave mirror.
Question 2.
Which mirror is used by dentists?
Question 3.
What are the advantages and disadvantages of using convex mirror for seeing traffic at the rear?
Question 4.
What are the advantages and disadvantages of using a convex mirror for seeing traffic at the rear?
Question 5.
The refractive index of diamond is 2.42. What is the meaning of this statement?
Question 6.
A ray is incident along ACB on a spherical mirror, where C is the centre of curvature.
Question 7.
Find the focal length of a convex mirror whose radius of curvature is 32 cm.
Question 8.
Why do we prefer a convex mirror as a rear- view mirror in vehicles?
Question 9.
What happens when the rays of sun are focused at a point on the paper by using concave mirror?
Question 10.
How is the refractive index of an optical medium related to the speed of light in that medium?
Question 11.
Define the term absolute refractive index of a medium.

1. The point on the principal axis where all the incident rays ,parallel to the principal axis actually meet after reflection from the concave mirror
2. Concave mirrors
5. It means ratio of speed of light in air to the speed of light in diamond is equal to 2.42
7.focal length =32/2 = 16 cm
8. Two reasons
i. It always produced erect and virtual image
ii. The size of the image is smaller then the object.
Both of the above reason allows the driver to have a wider view of the traffic behind the vehicle in small mirror
9. The paper burns due to converging of the light at that point.
10. Refractive index of an optical medium is ratio speed of the light in air to the speed of the light in the optical medium
11. Absolute refractive index of a medium is defined as the ratio of the velocity of light in vacuum to the velocity of light in the medium. If c is the velocity of light in vacuum and v in the medium, then n = c/v

## Short Answer type (2 marks each)

Question 1.
Name the type of mirror used in the following situations:
ii.Side/rear view mirror of a vehicle.
iii.Solar furnace.
Question 2.
Show that the mirror formula for spherical mirrors also holds for a plane mirror too.
Question 3.
A concave mirror produces three times magnified real image of an object placed at 10 cm in front of it. Where is the image located?
Question 4.
Light enters from air to glass having refractive index 1.50. What is the speed of light in the glass? The speed of light in vacuum is $3 \times 10^8 m/s$
Question 5.
Name the type of mirror which is known as shaving mirror. Give relevant ray diagram to justify your answer.
Question 6.
Find the focal length in cm of a lens of power -2D. Identify the type of this lens in this case.
Question 7.
Find the refractive index of glass with respect to water where refractive index of glass with respect to air is $n_{ga} = \frac {3}{2}$ and that of water with respect to air is $n_{wa} = \frac {4}{3}$.
Question 8.
A converging lens has a focal length of 250 mm. Calculate its power and express it according to sign convention.
Question 9.
List four specific characteristics of the images of the object formed by convex mirrors.
Question 10.
State two positions in which a concave mirror produces a magnified image of a given object. List two differences between the two images.
Question 11.
State the meaning of linear magnification. How is it related to object distance and image distance? When is magnification positive or negative?

1. a. Concave mirror
b. convex mirror
c. concave mirror

2.
Spherical Mirror formula is given as
$\frac {1}{f} = \frac {1}{v} + \frac {1}{u}$
For a plane mirror, $f = \infty$ , v = v , u = -v
Applying these to Mirror formula
$\frac {1}{\infty} = \frac {1}{v} + \frac {1}{-v}$
$0 = 0$
Hence mirror formula holds good for plane mirrors too.

3.
Here, linear magnification (m) = - 3 (Negative sign for real image, which is inverted)
Object distance(u)=-10 cm
Image distance =x
Now $m= -\frac {v}{u}$
or v =3u =-30 cm
The image is located at 30 cm in front of the mirror.

4. Refractive index is given by
$n= \frac { speed \; light \; in \; air}{speed \; light \; in \; glass}$
$1.5 = \frac {3 \times 10^8 }{x}$
$x=2 \times 10^8$

5. Concave mirror

6. $Power = \frac {1}{f(m)}$
$f(meter) = \frac {1}{power} = -.5 m$
f=-50 cm. It is a concave lens

7. $n_{gw}= \frac {n_{ga}}{n_{wa}}$
$= \frac {3/2}{4/3} = \frac {9}{8}$

8. f=250 mm = .25 m
$Power = \frac {1}{f(m)} = 4 D$

9.
i.The image is always virtual and erect.
ii.The image is highly diminished or point sized.
iii.It is always formed between F and P.
iv. The object and image are on opposite sides of mirror.

10.
A concave mirror produces a magnified image when the object is placed in front of the mirror:
i.between its pole and focus
ii.between the focus and centre of curvature
For Ist one the image is virtual and erect, whereas in second the image is real and inverted.

11.
linear magnification is the ratio of the size of the image to the size of the object . It is denoted by Letter m.
For a mirror ,formula is given
$m = - \frac { v }{ u}$
For a lens ,formula is given
$m = - \frac { v }{ u}$
If the image formed is virtual then the magnification has positive value and in case of real images, it is negative

## Fill in the blanks(1 Marks)

1. The refractive index of a medium gives an indication of the ……………Ability of that medium
2. When a ray of light goes from water to air, it bends …………From the normal
3. When a ray of light goes from air to glass, it bends ………The normal
4. The speed of light is …… in glass then air
5. The absolute refractive index is always ….. then unity
6. The relative refractive index can be less then ………

Fill in the blanks
(1)Bending
(2) Away
(3) towards
(4) less
(5) Greater
(6) Unity

## Crossword Puzzle

Across
3. The human eye forms the image at this point
5. The medium where speed of light is less
8. A instrument which is used to see details of distant objects
10. The refractive index is equal to reciprocal of the sine of this angle
Down
1. A optical instrument which is used to see small objects
2. It is produced by the dispersion of sunlight by the rain drops in the air
4. The nature of the image formed by the convex lens when the object is placed between optical center and focus
5. The size of the image formed by the concave lens
6. A converging lens
7. It is the defect of eye when it cannot see distant objects clearly
9. The lens having negative power

Crossword solution
Across
Retina, Denser , Telescope ,Critical
Down
Microscope, Rainbow , Virtual , Diminished ,Convex. Myopia, Concave,

## Long Answer type (5 marks each)

Question 1.
With the help of ray diagrams, show the formation of images of an object by a concave mirror. When it is placed
(i)beyond the centre of curvature
(ii)at the centre of curvature.

Question 2.
Draw ray diagrams to show the formation of image by an object by a concave lens when the object is placed
(i)at infinity
(ii)between infinity and optical centre of the lens.

Question 3.
Draw a labelled ray diagram to locate the image of an object formed by a convex lens of Focal length 20 cm when the object is placed 30 cm away from the lens.

Question 4.
(i)What is meant by the power of a lens?
(ii)What is its SI unit?
(iii) Name the type of lens whose power is positive.
(iv) The image of an object formed by a lens is real, inverted and of the same size as the object. If the image is at a distance of 40 cm from the lens, what is the nature and power of the lens? Draw ray diagram to justify your answer.

(i) Power of lens is the ability of a lens to converge or diverge light rays and it is equal to Reciprocal of focal length of the lens
(ii) S.I. unit is dioptre
(iii) Convex lens has positive power
(iv) v= +40 cm; h' = h The lens is real, inverted and same sized
u =-v
Using lens Formula,
$\frac {1}{f} = \frac {1}{v} -\frac {1}{u}$
2f=v or f=20 cm
It is a convex lens

Question 5.
One half of a convex lens of focal length 10 cm is covered with a black paper. Can such a lens produce an image of a complete object placed at a distance of 30 cm from the lens? Draw a ray diagram to justify your answer.

Question 6.
With the help of a ray diagram, state and explain the laws of reflection of light at a plane mirror. Mark the angle of incidence and reflection clearly in the diagram. If the angle of incidence is 32.5o, what will be the angle of reflection?

Question 7.
Why does a light ray incident on a rectangular glass slab immersed in any medium emerge parallel to itself? Explain using a diagram.

## Summary

This Light Reflection and Refraction Class 10 Worksheet with answers 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.