Light Energy ICSE Class-7th Concise Selina Physics Solutions Chapter-4. We Provide Step by Step Answer of Objective, True False , Fill in the blanks,Match the following , Short/Long Answer Type of Exercise-4 Light Energy. Visit official Website  CISCE  for detail information about ICSE Board Class-7.

## A. Objective Questions

1. Write true or false for each statement

(a) The image formed by a plane mirror is real.
The image formed by a plane mirror is virtual.

(b) When a light ray is reflected from a wall, the angle of incidence is not equal to the angle of reflection.
When a light ray is reflected from a wall, the angle of incidence is 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.

(c) The image formed by a plane mirror can be obtained on a screen.

(d) The image formed by a plane mirror is upright.

(e) The image formed by a plane mirror can be obtained on a screen.

(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.

(c) The image formed by a plane mirror can be obtained on a screen.

### 2. Fill in the blanks Light Energy ICSE Class-7th

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

### 4. Select the correct alternative Light Energy ICSE Class-7th Physics solutions

(a) A man standing in front of a plane mirror finds his image to be at a distance of 6 metre from himself. The distance of man from the mirror is

1. 6 m
2. 3 m
3. 2 m
4. 12 m

3 m

(b) The angle between the incident ray and the ray reflected from the plane mirror is 70°. The angle of incidence will be :

70°
30°
35°
90°

35°

(c) The image formed by a plane mirror is

virtual and inverted
virtual and of same size
real and inverted
real and of same size

virtual and of same size

(d) The angle of incidence on a plane mirror is 30°.The angle of reflection will be:

30°
60°
15°

30°
(e) The angle of incidence on a plane mirror is 30°. The angle between the incident ray and the reflected ray is

30°
15°
60°
90°

60°

(f) The property due to which a light ray striking a surface is returned back into the same medium is called

refraction
reflex action
reflection
regression

reflection

(g) A ray of light after reflection from a mirror is known as

reflected ray
normal
incident ray
refracted ray

reflected ray

(h) The speed of light is maximum in

glass
water
air
wood

air
(i) A red rose is seen in green light. It will appear.

red
blue
yellow
black

black

(j) The primary colours are

Red, Blue and Yellow
Magenta, Yellow and Cyan
Red, Blue and Cyan
Blue, Green and Red

Blue, Green and Red

### B. Short/Long Answer Questions Light Energy ICSE Class-7th

#### Question 1.

What do you mean by the term reflection of light ?
Reflection of light— When light strikes a polished surface it comes back in the same medium, is called reflection of light.

#### Question 2.

How is a plane mirror made ?
To make a plane mirror, a thin piece of glass is taken. One surface of the mirror is made opaque by silvering it. On the top of that, another thin coating of red lead oxide is given which protects the silvering of the mirror.

#### Question 3.

Explain the following terms:
Incident ray, Reflected ray, Angle of incidence, Angle of reflection, Normal.
Incident ray— The ray of light falling on the surface AB is called the incident ray. In figure PN is the incident ray.
Reflected ray— The incident ray bouncing back in the same medium after striking the reflecting ourface is called reflected ray. In figure NQ is the reflected ray.

Angle of incidence— The angle formed between the incident ray and the normal is the angle of incidence. (PNM is the angle of incidence.)
Angle of reflection— The angle formed between the normal and the reflected ray is called angle of reflection (MNQ is the angle of reflection)
Normal— It is the line drawn perpendicular to the reflecting surface at the point of incidence. MN is the normal.

#### Question 4.

Draw 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.
AO is the incident ray
OB is the reflected ray

ON is the normal
∠AON is the angle of incidence
∠NOB is the angle of reflection.

#### Question 5.

State the two laws of reflection of light.
Laws of reflection—
(i) The incident ray, normal and the reflected ray all lie in the same plane.
(ii) The angle of incidence is equal to the angle of reflection.

#### Question 6.

Describe an experiment to verify the laws of reflection of light. Ans. Laws of reflection.
(i) The incident ray, the reflected ray and the normal at the point of incidence, lie in the same plane.
(ii) The angle of incidence and angle of reflection are equal i.e. ∠i = ∠r.
Verification

Take a wooden drawing board and fix a white sheet of paper on it. In the middle of paper draw a straight line KK\ Mark a point B on it. Draw a perpendicular BN. Place a mirror XX’ on line KK’ such that polished side of mirror is along the line. Hold-the mirror in the mirror holder.

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