NCERT Exemplar for Class 8 Science Solutions Chapter 16 Light

Multiple Choice Questions

1. Parts of the eye which controls the light entering is called

a) Iris

b) Cornea

c) Lens

d) Retina

Ans: The part of the eye that controls the amount of light entering the eye is iris. It controls the aperture of the eye regulating the amount of light that can enter. Hence, option (a) is the correct answer. 

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.

Ans: The objects which have their own light are called luminous objects and are easily visible to us. The objects which do not emit their own light are called non-luminous objects and we can see them when the light is reflected from the object towards our eye. Hence, option (b) is the correct answer. 

3. Light is falling on the surface \[{S_1}\], \[{S_2}\], \[{S_3}\] as shown in Fig. 16.1. 

Surfaces on which the angle of incidence is equal to the angle of reflection is/are

(a) \[{S_1}\] only 

(c) \[{S_1}\] and \[{S_2}\] only 

(b) \[{S_2}\] and \[{S_3}\]

(d) all the three surfaces

Ans: Laws of reflection are applicable on any surface. Hence, (d) option is the correct answer. 

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 the eye with respect to the position of the bulb is shown in Fig. 16.2 as A, B, C, and D. In which position will the mirror be visible?

Ans: According to the laws of reflection, angle of incidence is equal to the angle of reflection. Hence, option A is the correct answer. 

5. A small hole P is made in a piece of cardboard. The hole is illuminated by a torch as shown in Fig. 16.3. 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

b) B

c) C

d) D

Ans: The eye should be placed at position A as the angle of incidence is equal to the angle of reflection. 

6. Two mirrors A and B are placed at right angles to each other as shown in Fig. 16.4. A ray of light incident on mirror A at an angle of \[{25^ \circ }\] falls on mirror B after reflection. The angle of reflection for the ray reflected from mirror B would be

a) \[{25^ \circ }\]

b) \[{50^ \circ }\]

c) \[{65^ \circ }\]

d) \[{115^ \circ }\]

Ans: Both the mirrors are inclined to each other at \[{90^ \circ }\]. This means that the normal of both the mirrors will also be perpendicular to each other. We know that the angle of incidence is equal to the angle of reflection. Hence, the angle made by a reflected ray with normal is \[{25^ \circ }\]. 

Hence, \[x + {25^ \circ } = {90^ \circ }\]

\[x = {65^ \circ }\]

Option c is the correct answer. 

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.

Ans: Rod cells cannot sense colour because they are sensitive to dim lights. Cone cells are sensitive to bright light and hence can detect colour. 

8. In the figure of the human eye (Fig. 16.5), the cornea is represented by the letter 

(a) A 

(b) B 

(c) C 

(d) D

Ans: A represents the iris of the eye. B represents the eye lens and C represents the cornea. Hence, option c is the correct answer. 

Very Short Answer Questions

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

Ans: Iris gives colour to eyes.

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?

Ans: The image of any object we see remains on the retina of our eye for one-sixteenth seconds. This is called the persistence of vision. When Boojho waves his hand very fast, it appears as if his fingers are moving and hence his fingers appear blurred to him. 

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

Ans: A ray of light can be reflected an infinite number of times by two plane mirrors placed parallel to each other. 

12. The angle between the incident ray and reflected ray is \[{60^ \circ }\]. What is the value of angle of incidence?

Ans: The angle made between the reflected ray and incident ray includes the angle of incidence and angle of reflection. So, we have, \[i + r = {60^ \circ }\].

Also, we know that angle of incidence is equal to angle of reflection. 

So, we have, \[i = r\].

Therefore, \[i + i = {60^ \circ }\]

\[i = \dfrac{{{{60}^ \circ }}}{2} = {30^ \circ }\]

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?

Ans: The distance between object and image includes the distance between image and mirror and the distance between object and mirror. In the case of a plane mirror, the distance between the plane mirror and object is equal to the distance between the plane mirror and image. Let the distance from the image to the mirror be x.

Then, the distance from the object to mirror is also x.

So, \[x + x = 24cm\]

\[x = 12cm\]

Hence, the distance between the mirror and the object is \[12cm\].

Short Answer Questions

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

Ans: Light splits into the constituent colours when it gets dispersed. The formation of the rainbow is an example of the dispersion of white light. 

15. Draw Fig. 16.6 showing the position of the plane mirror. Also, label the angle of incidence and angle of reflection on it.

Ans: Ray A is incident ray and ray B is reflected ray. Hence, angle x is the incident angle and angle y is the reflected angle. 

16. Look at Fig. 16.7. Can the image of the child in it be obtained on a screen?

Ans: Images formed in a plane mirror are virtual. Virtual images cannot be obtained on a screen. Therefore, it is not possible to obtain the image of a child on a screen. 

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

Ans: Eyes of the nocturnal birds have large cornea and large pupils as this structure helps them to collect colours on a wider range and enables them to see even in dark surroundings. 

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

Ans: The lens of our eyes from the image on the retina. A convex lens is there in our eyes. 

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

Ans: The lens of the human eye gets cloudy when a person suffers from a cataract. Cataracts can be treated by replacing the clouded and blurry lens with a new clear artificial lens. 

Long Answer Questions

20. Boojho planned an activity to observe an object A through pipes as shown in Fig. 16.8, so that he could see objects which he could not directly see. 

(a) How many mirrors should he use to see the objects? 

Ans: Three plane mirrors should be used by Boojho to see the objects. 

(b) Indicate the positions of the mirrors in the figure. 

Ans: The positions of the mirrors as shown in the figure.

(c) What must be the angle with respect to the incident light at which he should place the mirrors? 

Ans: \[{45^ \circ }\]

(d) Indicate the direction of rays in the figure. 

Ans: The direction of rays are as shown in the figure. 

(e) If any of the mirrors is removed, will he be able to see the objects?

Ans: No, Boojho won’t be able to see the object if any of the mirrors is removed. 

21. There is a mistake in each of the following ray diagrams given as Fig. 16.9 a, b, and c. Make the necessary correction(s). 

Ans: The angles are labelled wrongly in diagram (a). The angle of reflection is labelled as angle of incidence and vice versa. In diagram (b), the law of reflection is not followed as angle of reflection and angle of incidence are not equal in measure. The normal drawn is not perpendicular to the surface in diagram (c). 

The corrected ray diagram is as shown below. 

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

Ans: The image that we see through our eyes remains there on the retina for one-sixteenth of a second. This is called the persistence of image. Hence, if the series of static images is shown to us at a pace greater than our persistence of image, they appear to be in motion. Cartoon films are made to move at twenty-four frames per second which enables us to perceive motion in a cartoon film. 

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

Ans: The mirrors inclined to each other in Kaleidoscope form a number of images through reflection. It is used to get ideas from designers and artists to create new designs. 

24. Fig. 16.10 shows the word REST written in two ways in front of a mirror. Show how the word would appear in the mirror. 

Ans:

25. Write down the names of parts of the eye in the blank spaces shown in Fig. 16.10.

Ans: 

The part of the eye labelled with (1) is the Ciliary muscle.

The part of the eye labelled with (2) is Iris.

The part of the eye labelled with (3) is Lens.

The part of the eye labelled with (4) is Cornea.

The part of the eye labelled with (5) is Retina.

The part of the eye labelled with (6) is the Optic nerve.

About NCERT Chapter 16 Light

NCERT Exemplar Class 8 Science Solutions Chapter 16 Light gives you crucial information on the types and levels of difficulty of questions that are commonly asked in CBSE Class 8 exams and a few competitive examinations. As a result, applicants must become familiar with the NCERT Exemplar Solution. There are multiple-choice problems, match the column, fill in the gaps, short answer questions, extremely short answer problems, long answer questions, and numerical problems among the questions in this section.

Light is a type of electromagnetic radiation that falls within a specific range of frequencies. The students will study the various qualities of light and its sources in this chapter. They will also be taught about the principles of reflection and how the human eye perceives images.

NCERT Exemplar Class 8 Science Chapter 16 Light: Important Topics

What causes things to be visible?

Reflection Laws, Regular and Diffused Reflection, and Reflected Light Can Be Re-Reflected

Sunlight - White or Colored, Multiple Images

What's on the Inside of Our Eyes, Eye Care,

People with visual impairments can read and write.

What is the Braille System, and how does it work?

Vedantu keeps track of all of each student's development as part of the overall package. Following an assessment of the issue, regular input is provided. We also offer a responsive support team to answer any questions you may have. Students can ask any question they have about any subject and get it solved by the top faculties of Vedantu