NCERT Solutions for Class 10 Science Unit 10

Light - Reflection and Refraction Class 10

Unit 10 Light - Reflection and Refraction Exercise Solutions

Reflection :- The bouncing back of rays of light from a polished and shiny surface is called reflection or reflection of light. It is similar to bouncing back of a football after colliding with a wall or any hard surface.

Refraction :- The change of direction of light because of change of medium is known as Refraction or Refraction of Light. The ray of light changes its direction or phenomenon of refraction takes place because of difference in speed in different media. The light travels at faster speed in rare medium and at slower speed in denser medium. The nature of media is taken as relative. For example air is a rarer medium than water or glass. When ray of light enters from a rarer medium into a denser medium, it bends towards normal at the point of incidence. On the contrary, when ray of light enters into a rarer medium from a denser medium it bends away from the normal. Ray emerging after the denser medium goes in the same direction and parallel to the incident ray.
<< Previous Chapter 9 : Heredity and Evolution Next Chapter 11 : Human Eye and Colourful World >>

Question : Solutions of Questions on Page Number : 168

Q1 :  

Define the principal focus of a concave mirror.


Answer :

Light rays that are parallel to the principal axis of a concave mirror converge at a specific point on its principal axis after reflecting from the mirror. This point is known as the principal focus of the concave mirror.

Answer needs Correction? Click Here

Q2 :  

The radius of curvature of a spherical mirror is 20 cm. What is its focal length?


Answer :

Radius of curvature, R= 20 cm

Radius of curvature of a spherical mirror = 2 × Focal length (f)

R= 2f

Hence, the focal length of the given spherical mirror is 10 cm.

Answer needs Correction? Click Here

Q3 :  

Name the mirror that can give an erect and enlarged image of an object.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q4 :  

Why do we prefer a convex mirror as a rear-view mirror in vehicles?


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q5 :  

Find the focal length of a convex mirror whose radius of curvature is 32 cm.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q6 :  

A concave mirror produces three times magnified (enlarged) real image of object placed at 10 cm in front of it. Where is the image located?


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q7 :  

Aray of light travelling in air enters obliquely into water. Does the light ray bend towards the normal or away from the normal? Why?


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q8 :  

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 x 108 m s-1.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q9 :  

Find out, from Table, the medium having highest optical density. Also find the medium with lowest optical density.

Material

medium

Refractive index

Material medium

Refractive

index

Air

1.0003

Canada Balsam

1.53

Ice

1.31

-

-

Water

1.33

Rock salt

1.54

Alcohol

1.36

-

-

Kerosene

1.44

Carbon disulphide

1.63

Fused

quartz

1.46

Dense

flint glass

1.65

Turpentine oil

1.47

Ruby


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q10 :  

You are given kerosene, turpentine and water. In which of these does the light travel fastest? Use the information given in Table.

Material

medium

Refractive index

Material medium

Refractive

index

Air

1.0003

Canada Balsam

1.53

Ice

1.31

-

-

Water

1.33

Rock salt

1.54

Alcohol

1.36

-

-

Kerosene

1.44

Carbon disulphide

1.63

Fused

quartz

1.46

Dense

flint glass

1.65

Turpentine oil

1.47

Ruby

1.71

Benzene

1.50

Sapphire

1.77


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q11 :  

The refractive index of diamond is 2.42. What is the meaning of this statement?


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q12 :  

Define 1 dioptre of power of a lens.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q13 :  

A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it. Where is the needle placed in front of the convex lens if the image is equal to the size of the object? Also, find the power of the lens.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q14 :  

Find the power of a concave lens of focal length 2 m.


Answer :

Please Register/Login to get access to all solutions Facebook Login
<< Previous Chapter 9 : Heredity and Evolution Next Chapter 11 : Human Eye and Colourful World >>

Exercise : Solutions of Questions on Page Number : 185

Q1 :  

Which one of the following materials cannot be used to make a lens?

(a) Water

(b) Glass

(c) Plastic

(d) Clay


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q2 :  

The image formed by a concave mirror is observed to be virtual, erect and larger than the object. Where should be the position of the object?

(a) Between the principal focus and the centre of curvature

(b) At the centre of curvature

(c) Beyond the centre of curvature

(d) Between the pole of the mirror and its principal focus.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q3 :  

Where should an object be placed in front of a convex lens to get a real image of the size of the object?

(a) At the principal focus of the lens

(b) At twice the focal length

(c) At infinity

(d) Between the optical centre of the lens and its principal focus.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q4 :  

A spherical mirror and a thin spherical lens have each a focal length of -15 cm. The mirror and the lens are likely to be

(a) both concave

(b) both convex

(c) the mirror is concave and the lens is convex

(d) the mirror is convex, but the lens is concave


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q5 :  

No matter how far you stand from a mirror, your image appears erect. The mirror is likely to be

(a) plane

(b) concave

(c) convex

(d) either plane or convex


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q6 :  

Which of the following lenses would you prefer to use while reading small letters found in a dictionary?

(a) A convex lens of focal length 50 cm

(b) A concave lens of focal length 50 cm

(c) A convex lens of focal length 5 cm

(d) A concave lens of focal length 5 cm


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q7 :  

We wish to obtain an erect image of an object, using a concave mirror of focal length 15 cm. What should be the range of distance of the object from the mirror? What is the nature of the image? Is the image larger or smaller than the object? Draw a ray diagram to show the image formation in this case.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q8 :  

Name the type of mirror used in the following situations.

(a) Headlights of a car

(b) Side/rear-view mirror of a vehicle

(c) Solar furnace

Support your answer with reason.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q9 :  

One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q10 :  

An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and the nature of the image formed.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q11 :  

A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens? Draw the ray diagram.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q12 :  

An object is placed at a distance of 10 cm from aconvex mirror of focal length 15 cm. Find the position and nature of the image.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q13 :  

The magnification produced by a plane mirror is +1. What does this mean?


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q14 :  

An object 5.0 cm in length is placed at a distance of 20 cm in front of a convex mirror of radius of curvature 30 cm. Find the position of the image, its nature and size.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q15 :  

An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen be placed, so that a sharp focused image can be obtained? Find the size and the nature of the image.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q16 :  

Find the focal length of a lens of power -2.0 D. What type of lens is this?


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q17 :  

A doctor has prescribed a corrective lens of power +1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging?


Answer :

Please Register/Login to get access to all solutions Facebook Login
<< Previous Chapter 9 : Heredity and Evolution Next Chapter 11 : Human Eye and Colourful World >>

Science : CBSE NCERT Exercise Solutions for Class 10th for Light - Reflection and Refraction will be available online in PDF book form soon. The solutions are absolutely Free. Soon you will be able to download the solutions.

Popular Articles
Question
Question 1
Question 2
Question 3
Question 4
Question 5
Question 6
Question 7
Question 8
Question 9
Question 10
Question 11
Question 12
Question 13
Question 14
Exercise
Question 1
Question 2
Question 3
Question 4
Question 5
Question 6
Question 7
Question 8
Question 9
Question 10
Question 11
Question 12
Question 13
Question 14
Question 15
Question 16
Question 17