Selina solutions concise physics class 7 icse Solutions for Chapter 4 light energy

Q1) Write 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 are seen around us due to irregular reflection of light

(g) The speed of light in vacuum is 3 108 ms-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.

Q2) Fill in the blanks .

(a) Angle of incidence = ___________.

(b) The incident ray, the reflected ray and the normal lie in one ______.

(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 erect 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.

Q3) Match the following :

Q4) Select the correct alternative :

(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. 3m

3. 2 m

4. 12 m

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

1. 70°

2. 30°

3. 35°

4. 90°

(c) The image formed by a plane mirror is

1. virtual and inverted

2. virtual and of same size

3. real and inverted

4. real and of same size

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

1. 30°

2. 60°

3. 1°

4. 0°

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

1. 30°

2. 15°

3. 60°

4. 90°

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

1. refraction

2. reflex action

3. reflection

4. regression

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

1. reflected ray

2. normal

3. incident ray

4. refracted ray

(h) The speed of light is maximum in

1. glass

2. water

3. air

4. refracted ray

(i) A red rose is seen in green light. It will appear.1. red

2. blue

3. yellow

4. black

(j) The primary colours are

1. Red, Blue and Yellow

2. Magenta, Yellow and Cyan

3. Red, Blue and Cyan

4. Blue, Green and Red

Q1) What do you mean by the term reflection of light?

Q2) How is a plane mirror made?

Q3) Explain the following terms : Incident ray, reflected ray, angle of incidence, angle of reflection, normal

Q4) 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.

Q5) State the two laws of reflection of light.

Q6) Describe an experiment to verify the laws of reflection of light and laws of reflection

Q7) A ray of light falls normally on a plane mirror. What is the angle of incidence?

Q8) Draw a diagram to show the reflection of a light ray incident normally on a plane mirror.

Q9) The diagram in fig. 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 :

(i) the angle of incident

(ii) the angle of reflection

Q10) In the following diagrams, measure and write the angle of incidence and draw the reflected ray in each case.

Q11) The diagram in fig. 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.

Q12) The following diagram shows an incident ray AO and the normal ON on a plane mirror. Find the angle of incidence and angle of reflection.

Q13) State in words, how do you find the location of an image of an object formed by a plane mirror?

Q14) Draw a ray diagram showing the formation of a point object by a plane mirror.

Q15) The 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.

Q16) State four characteristics of the image formed by a plane mirror.

Q17) How is the position of image formed by a plane mirror related to the position of the object ?

Q18) You 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 ?

Q19) What is meant by lateral inversion of an image mirror? Explain it with the help of a diagram.

Q20) Write down the letter C and I as seen in a plane mirror.

Q21) What is irregular reflection? Give an example.

Q22) How do we see objects around us ?

Q23) State two uses of a plane mirror?

Q24) Can light travel in vacuum?

Q25) State the speed of light in (a) air (b) glass.

Q26) State whether light slows down or speeds up in the following cases:

(a) light going from air to glass

(b) light going from glass to water

(c) light going from water to air

Q27) What are the primary colours ? name the three primary colours.

Q28) What are the secondary colours ? name the three secondary colours.

Q29) Fill in the blanks with the appropriate colors (a) blue + ……….. = cyan (b) red +blue + ……….. = white (c) red + blue = ……….. (d) green + red = ………..

Q30) The leaves appear green when seen in white light. Give a reason.

Q31) A rose appears red in white light. How will it appear in (i) green light (ii) red light ? Give a reason for your answer for each.

Q32) Why does a piece of paper appear white in sunlight? How would you expect it to appear when viewed in red light?

Q33) A piece of paper appears black in sunlight. What will be its color when seen in red light ?