Question 1

Question 1Write true or false for each statement:(a) The image formed by a plane mirror is real.(b) When a light ray is reflected from a wall, the angle of incidence is not equal to the angle of reflection.(c) The image of the right hand in a plane mirror looks like that of a left hand.(d) The image formed by a plane mirror is upright.(e) The image formed by a plane mirror can be obtained on a screen.(f) The objects around us are seen due to irregular reflection of light.(g) The speed of light in vacuum is 3 x 108 m s-1.(h) A rose appears red in light of all the colours.(i) A black paper absorbs light of all the colours and reflects none.(j) The primary colours are red, blue and green.

Accepted Answer

(a) FalseCorrect Statement — The image formed by a plane mirror is virtual.(b) FalseCorrect Statement — When a light ray is reflected from a wall, the angle of incidence is equal to the angle of reflection.(c) True(d) True(e) FalseCorrect Statement — The image formed by a plane mirror cannot be obtained on a screen.(f) True(g) True(h) False A rose appears red in white light. Correct Statement —(i) True(j) True

Question 2

Question 2Fill in the blanks:(a) Angle of incidence = ...............(b) The incident ray, the reflected ray and the normal lie ...............(c) The image formed by a plane mirror is at a distance behind the mirror as ............... .(d) The image formed by a plane mirror is ............... and ............... .(e) We are able to see the objects around us due to ............... reflection.(f) A ............... image cannot be obtained on a screen.(g) One surface of mirror is made opaque by ............... it followed by a thin coating of paint of lead oxide.(h) A plane mirror ............... reflect 100 percent light falling on it.(i) The colour of an opaque object is the colour of light which it ............... .(j) Magenta, cyan and yellow are the ............... colours.

Accepted Answer

(a) Angle of reflection(b) in one plane(c) the object is in front of it(d) erect, virtual(e) irregular(f) virtual(g) silvering(h) does not(i) reflects(j) secondary

Question 3

Question 4dThe angle of incidence on a plane mirror is 30°. The angle of reflection will be:30°60°15°0°

Accepted Answer

30°Reason — The angle of incidence = angle of reflection.

Question 4

Question 3Explain the following terms:Incident rayReflected rayAngle of incidenceAngle of reflectionNormal

Accepted Answer

The ray of light that strikes the surface is called the incident ray.The ray of light which is returned back into the same medium after striking the reflecting surface is called the reflected ray.The angle between the incident ray and the normal is called the angle of incidence. It is represented by the letter i.The angle between the reflected ray and the normal is called the angle of reflection. It is represented by the letter r.The perpendicular drawn on the surface at the point of incidence is called the normal.

Question 5

Question 4Draw a diagram showing the reflection of a light ray from a plane mirror. Label on it the incident ray, the reflected ray, the normal, the angle of incidence i and the angle of reflection r.

Accepted Answer

Below is the labelled diagram showing the reflection of a ray of light by a plane mirror:

Question 6

Question 5State the two laws of reflection of light.

Accepted Answer

The two laws of reflection of light are:The angle of incidence is equal to angle of reflection.The incident ray, the reflected ray and the normal all lie in the same plane.

Question 7

Question 6Describe an experiment to verify the laws of reflection of light.

Accepted Answer

The laws of reflection of light can be verified by the following experiment:Take a drawing board and a white sheet of paper. Fix the white sheet of paper on the drawing board. Draw a straight line MM1 on the paper.On the line MM1 take a point O at its middle and draw a line OA such that ∠MOA is less than 90°. Draw a normal ON on MM1 at point O.Take a small plane mirror and place along the line MM1. Use plasticine to fix the mirror on the paper so that it stands upright.Fix pins P and Q vertically on the line OA. Set your eye on the other side of the normal ON along the direction as shown in below figure.You will see images P', Q' of pins P and Q in the mirror.Set your eye in line with the two images P', Q' and fix two more pins R and S on the paper in front of the mirror such that both the pins R and S are in line with P', Q'.Remove the mirror and draw small circles around pins P, Q, R and S. Draw a line OB joining the points R and S.AO is incident ray, OB is reflected ray and ON is normal at the point of incidence O.Using a protractor measure angle of incidence i (∠AON), angle of reflection r (∠BON). We will find two angles are equal.This experiment verifies the two laws of reflection:Angle of incidence = Angle of reflection.Incident ray, reflected ray and normal all lie in the same plane of paper which is the second law of reflection.

Question 8

Question 8Draw a diagram to show the reflection of a light ray incident normally on a plane mirror.

Accepted Answer

Below diagram shows the reflection of a light ray incident normally on a plane mirror:

Question 9

Question 9The diagram shows an incident ray AO and the reflected ray OB from a plane mirror. The angle AOB is 30°. Draw normal on the plane mirror at the point O and find:(a) the angle of incidence(b) the angle of reflection.

Accepted Answer

(a) The angle of incidence is 15°.(b) The angle of reflection is 15°.

Question 10

Question 10In the following diagrams, measure and write the angle of incidence and draw the reflected ray in each case.

Accepted Answer

(a) Angle of incidence is 0°.(b) Angle of incidence is 30°.(c) Angle of incidence is 45°.

Question 11

Question 11The diagram shows an incident ray AO and the normal ON on a plane mirror. Draw the reflected ray. State the law you use to draw the direction of the reflected ray.

Accepted Answer

Below diagram shows the reflected ray:Law used to draw the direction of the reflected ray is:The angle of incidence is always equal to the angle of reflection.

Question 12

Question 12The following diagram shows an incident ray AO and the normal ON on a plane mirror. Find the angle of incidence and angle of reflection.

Accepted Answer

Normal ON is perpendicular on plane mirror, soAngle of incidence = 90° - 30° = 60°.Angle of reflection = 60°. (Since angle of incidence = angle of reflection)

Question 13

Question 13State in words, how do you find the location of image of an object formed by a plane mirror.

Accepted Answer

For an object in front of a plane mirror, the image is formed behind the mirror. The image is formed when the reflected rays are produced backwards. The image is as far behind the mirror as the object is in front of it.

Question 14

Question 14Draw a ray diagram showing the formation of image of a point object by a plane mirror.

Accepted Answer

Below ray diagram shows the formation of image of a point object by a plane mirror:

Question 15

Question 15The following diagram shows a point object O placed in front of a plane mirror. Take two rays from the point O and show how the image of O is formed and seen by the eye.

Accepted Answer

The ray diagram showing formation of the image of point object O placed in front of a plane mirror is given below:

Question 16

Question 16State four characteristics of the image formed by a plane mirror.

Accepted Answer

The four characteristics of the image formed by a plane mirror are:The image is upright or erect.The image is virtual.The image is of same size as the object.The image is laterally inverted.

Question 17

Question 17How is the position of image formed by a plane mirror related to the position of the object?

Accepted Answer

The image formed is as far behind the mirror as the object is in front of it.

Question 18

Question 18You are standing at a distance 2 metre from a plane mirror.(a) What is the distance of your image from the mirror?(b) What is the distance between you and your image?

Accepted Answer

(a) The distance of the image from the mirror is 2 metre as the image formed is as far behind the mirror as the object is in front of it.(b) The distance between object and image will be 4 m (object distance + image distance = 2 m + 2 m)

Question 19

Question 19What is meant by lateral inversion of an image in a plane mirror? Explain it with the help of a diagram.

Accepted Answer

The interchange of the left and right sides in the image of an object in a plane mirror is called lateral inversion.Below diagram illustrates lateral inversion of an image:

Question 20

Question 20Write down the letter C and I as seen in a plane mirror?

Accepted Answer

Letter C and I will appear as shown below, when seen in a plane mirror:

Light Energy

Objective Questions

Short/Long Answer Questions