Science Ncert_exemplar 2019 Solutions for Class 8 Science Chapter 16 Light are provided here with simple step-by-step explanations. These solutions for Light are extremely popular among Class 8 students for Science Light Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Science Ncert_exemplar 2019 Book of Class 8 Science Chapter 16 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Science Ncert_exemplar 2019 Solutions. All Science Ncert_exemplar 2019 Solutions for class Class 8 Science are prepared by experts and are 100% accurate.

Page No 90:

Question 1:

Part of the eye which controls the light entering is called
(a) iris                (c) lens
(b) cornea          (d) retina

Answer:

The dark muscular structure behind the cornea is called the iris, and it controls the amount of light entering into the eye.
Hence, the correct answer is option A.

Page No 90:

Question 2:

We can see a non-luminous object when light:
(a) emitted by the object falls on the eye.
(b) is reflected from the object towards our eye.
(c) completely passes through the object.
(d) gets completely absorbed by the object.

Answer:

When light is reflected from the non-luminous object towards our eye, it becomes visible to us.
Hence, the correct answer is option B.

Page No 90:

Question 3:

Light is falling on surface S1, S2, S3 as shown in the given figure.

Surfaces on which the angle of incidence is equal to the angle of reflection is/are
(a) S1 only                        (c) S2 and S3
(b) S1 and S2 only            (d) all the three surfaces

Answer:

Angle of incidence is equal to the angle of reflection for all the three surfaces S1, Sand S3, because laws of reflection are always followed irrespective of the surface of the object.
Hence, the correct answer is option D.



Page No 91:

Question 4:

A tiny mirror M is fixed on a piece of cardboard placed on a table. The cardboard is illuminated by light from a bulb. The position of eye with respect to position of bulb is shown in the given figure as A, B, C and D. In which position mirror will be visible?

a. A               c. C
b. B               d. D

Answer:

In case A, ray of light gets reflected back from the mirror, making angle of incidence and angle of reflection equal.
Hence, the correct answer is option A.



Page No 92:

Question 5:

A small hole P is made in a piece of cardboard. The hole is illuminated by a torch as shown in the given figure. The pencil of light coming out of the hole falls on a mirror.

At which point should the eye be placed so that the hole can be seen?
(a) A                 (c) C
(b) B                 (d) D

Answer:

The hole can be seen when reflected light comes to eye. According to law of reflection of light, angle of incidence is equal to angle to reflection, i.e. when the eye is placed at position  as shown in figure A, the hole can be seen.
Hence, the correct answer is option A.

Page No 92:

Question 6:

Two mirrors A and B are placed at right angles to each other as shown in the given figure.
A ray of light incident on mirror A at an angle of 250 falls on mirror B after reflection. The angle of reflection for the ray reflected
from mirror B would be
(a) 250     (c) 650
(b) 500     (d) 1150

Answer:


The ray of light reflected from mirror A is incident on mirror B with angle of incidence 650. Thus, the angle of reflection for the ray reflected from the mirror would also be 650.
Hence, the correct answer is option C. 



Page No 93:

Question 7:

Which of the following statements is correct regarding rods and cones in the human eye?
(a) Cones are sensitive to dim light.
(b) Cones are sensitive to bright light.
(c) Rods are sensitive to bright light.
(d) Rods can sense colour.

Answer:

Cones are sensitive to bright light, so they sense colour, but rods are sensitive to dim light and they cannot sense colour.
Hence, the correct answer is option B.

Page No 93:

Question 8:

In the figure of the human eye , the cornea is represented by the letter

(a) A            (c) C
(b) B            (d) D

Answer:

In the given figure, A represents Iris, B represents lens and C represents cornea.
Hence, the correct answer is option C.

Page No 93:

Question 9:

Name the part of the eye which gives colour to the eyes.

Answer:

Iris is the part of the eye which gives colour to the eyes.

Page No 93:

Question 10:

Boojho while waving his hand very fast in front of his eyes, observes that his fingers appear blurred. What could be the reason for it?

Answer:

Boojho while waving his hand very fast in front of his eyes, observes that his fingers appear blurred. It is due to persistence of vision.

Page No 93:

Question 11:

How many times is a ray of light reflected by two plane mirrors placed parallel and facing each other?

Answer:

A ray of light gets reflected infinite number of times by two plane mirrors placed parallel and facing each other.



Page No 94:

Question 12:

The angle between incident ray and reflected ray is 60°. What is the value of angle of incidence?

Answer:

According to laws of reflection, angle of incidence is equal to angle of reflection. So,
i=rand as given in the question, i+r=60°2i=60°i=30°
Thus, angle of incidence is 30o.

Page No 94:

Question 13:

The distance between the object and its image formed by a plane mirror appears to be 24 cm. What is the distance between the mirror and the object?

Answer:

In case of plane mirror, distance between the object and its image formed is twice as that of the distance between the mirror and the object.
So, Distance between the mirror and the object = 242 = 12 cm

Page No 94:

Question 14:

What happens to light when it gets dispersed? Give an example.

Answer:

Light splits into constituent colours when it gets dispersed. Rainbow is an example of it.

Page No 94:

Question 15:

In the given figure showing the position of the plane mirror. Also label the angle of incidence and angle of reflection on it.

Answer:

Angle of incidence (i) = angle of reflection (r
 

Page No 94:

Question 16:

Look at in the given figure. Can the image of the child in it be obtained on a screen?

Answer:

No, the image of the child cannot be obtained on a screen because it is a virtual image.



Page No 95:

Question 17:

Eyes of the nocturnal birds have large cornea and a large pupil. How does this structure help them?

Answer:

A large pupil and large cornea allows more light to enter their eyes which make them see objects even in faint light.

Page No 95:

Question 18:

What kind of lens is there in our eyes? Where does it form the image of an object?

Answer:

The type of lens in our eyes is convex. It forms image of the object on retina. 

Page No 95:

Question 19:

Which part of the eye gets affected if someone is suffering from cataract? How is it treated?

Answer:

The eye lens becomes clouded when someone suffers from cataract. It is treated by replacing the opaque lens with a new artificial lens.

Page No 95:

Question 20:

Boojho planned an activity to observe an object A through pipes as shown in the given figure, so that he could see objects which he could not directly see.

(a) How many mirrors should he use to see the objects?
(b) Indicate the positions of the mirrors in the figure.
(c) What must be the angle with respect to the incident light at which he should place the mirrors?
(d) Indicate the direction of rays in the figure.
(e) If any of the mirrors is removed, will he be able to see the objects?

Answer:

(a) He should use three mirrors to see the objects.
(b)
 
(c) He should place the mirrors at 450 with respect to the incident light.
(d)

(e) No, he will not be able to see the objects.

Page No 95:

Question 21:

There is a mistake in each of the following ray diagrams given as in the given figure a, b, and c. Make the necessary correction (s).

Answer:

The Figure in all the three cases after correction should be as :


Angle of incidence (i) = angle of reflection (r)



Page No 96:

Question 22:

Explain the process which enables us to perceive motion in a cartoon film.

Answer:

The cartoon film is actually the projection of static pictures on the screen in a specific order. When these static pictures are shown in a sequence at the rate of 24 pictures per second one after the other, they give us the perception of movement.

Page No 96:

Question 23:

How is the phenomenon of reflection used in making a kaleidoscope? What are the applications of a kaleidoscope?

Answer:

In kaleidoscope, the mirrors are inclined to one another and thus number of images gets formed by reflection from these mirrors. Kaleidoscope are used by designers and artists to get ideas for new patterns to design wallpapers, jewellery and fabrics.

Page No 96:

Question 24:

In the given figure shows the word REST written in two ways in front of a mirror. Show how the word would appear in the mirror.

Answer:

Page No 96:

Question 25:

Write down the names of parts of the eye in the blank spaces shown in the given figure.

Answer:

1. Ciliary muscle
2. Iris
3. Lens
4. Cornea
5. Retina
6. Optic Nerve



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