Q1Multiple choice
Part of the eye which controls the light entering is called
- (a)iris
- (b)cornea
- (c)lens
- (d)retina
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(a) iris
Chapter 16 – Light
Class 8 Science · 25 questions · 23 with answers
Questions
Q2Multiple choice
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.
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(b) is reflected from the object towards our eye.
Q3Multiple choice
Light is falling on surface S1, S2, S3 as shown in Fig.16.1. Fig.16.1 L IGHT 91 Surfaces on which the angle of incidence is equal to the angle of reflection is/are
This question refers to a figure in the original PDF.
- (a)S1 only
- (b)S1 and S2 only
- (c)S2 and S3
- (d)all the three surfaces
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(d) all the three surfaces
Q4Multiple choice
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 Fig.16.2 as A, B, C and D. In which position mirror will be visible? Bulb Eye Bulb Eye M M (A) (B) Bulb Bulb M M (C) (D) Fig. 16.2
This question refers to a figure in the original PDF.
- a.A
- b.B
- c.C
- d.D 92 E XEMPLAR PROBLEMS
Show answer
a. A
Q5Multiple choice
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. Fig. 16.3 At which point should the eye be placed so that the hole can be seen?
This question refers to a figure in the original PDF.
- (a)A
- (b)B
- (c)C
- (d)D
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(a) A
Q6Multiple choice
Two mirrors A and B are placed at right angles to each other as shown in Fig.16.4. Fig.16.4 L IGHT 93 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
This question refers to a figure in the original PDF.
- (a)25 0
- (b)50
- (c)65 0
- (d)1150
Show answer
(c) 65 0
Q7Multiple choice
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.
Show answer
(b) Cones are sensitive to bright light.
Q8Multiple choice
In the figure of the human eye (Fig.16.5), the cornea is represented by the letter Fig.16.5
This question refers to a figure in the original PDF.
- (a)A
- (b)B
- (c)C
- (d)D
Show answer
(c) C
Q9Very short answer
Name the part of the eye which gives colour to the eyes.
Show answer
Iris.
Q10Very short answer
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?
Show answer
Persistence of vision.
Q11Very short answer
How many times is a ray of light reflected by two plane mirrors placed parallel and facing each other? 94 E XEMPLAR PROBLEMS
Show answer
Infinite number of times.
Q12Very short answer
The angle between incident ray and reflected ray is 60°. What is the value of angle of incidence?
Show answer
30°.
Q13Very short answer
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?
Show answer
12 cm. SHORT ANSWER QUESTIONS
Q14Short answer
What happens to light when it gets dispersed? Give an example.
Show answer
Light is split into its constituent colours. Rainbow is an example.
Q15Short answer
Draw Fig.16.6 showing the position of the plane mirror. Also label the angle of incidence and angle of reflection on it. Fig.16.6
This question refers to a figure in the original PDF.
Q16Short answer
Look at Fig.16.7. Can the image of the child in it be obtained on a screen? Fig.16.7 L IGHT 95
This question refers to a figure in the original PDF.
Show answer
No, the image of the child cannot be obtained on a screen.
Q17Short answer
Eyes of the nocturnal birds have large cornea and a large pupil. How does this structure help them?
Show answer
A large pupil and large cornea allows more light to enter their eyes and they can see objects even in faint light.
Q18Short answer
What kind of lens is there in our eyes? Where does it form the image of an object?
Show answer
The type of lens in our eyes is convex. It forms images on the retina. 150 E XEMPLAR PROBLEMS
Q19Short answer
Which part of the eye gets affected if someone is suffering from cataract? How is it treated?
Show answer
In people suffering from cataract the eye lens becomes clouded. Cataract is treated by replacing the opaque lens with a new artificial lens. LONG ANSWER QUESTIONS
Q20Multiple choice
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. Fig. 16.8
This question refers to a figure in the original PDF.
- (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?
Show answer
(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?
Q21Multiple choice
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).
This question refers to a figure in the original PDF.
- (a)
- (b)
- (c)Fig. 16.9 96 E XEMPLAR PROBLEMS
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The Fig. in all the three cases after correction should be as in the given Fig. ANSWERS 151
Q22Long answer
Explain the process which enables us to perceive motion in a cartoon film.
Show answer
The cartoon film we see is actually the projection of static pictures on the screen in a specific order. Usually the static pictures are shown in a sequence at the rate of 24 pictures per second one after the other giving us the perception of movement.
Q23Long answer
How is the phenomenon of reflection used in making a kaleidoscope? What are the applications of a kaleidoscope?
Show answer
The kaleidoscope gives a number of images formed by reflection from the mirrors inclined to one another. Designers and artists use kaleidoscope to get ideas for new patterns to design wallpapers, Jewellery and fabrics.
Q24Long answer
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. Fig. 16.10
This question refers to a figure in the original PDF.
Q25Long answer
Write down the names of parts of the eye in the blank spaces shown in Fig. 16.10. 2 6 Fig. 16.11
This question refers to a figure in the original PDF.
Show answer
1. Ciliary muscle 2. Iris 3. Lens 4. Cornea 5. Retina 6. Optic Nerve 152 E XEMPLAR PROBLEMS