NCERT Exemplar Solution Class 8 Science Chapter 16
NCERT Exemplar Solution Class 8 Science Chapter 16 Light all Questions Answer Solution. NCERT Exemplar Class 8 Science Chapter 16 Solution PDF.
NCERT Exemplar Solution Class 8 Science Chapter 16: Overview
NCERT Exemplar Solution Class 8 Science Chapter 16 |
|
Board |
NCERT |
Topic |
Exemplar Problem Solution |
Class |
8 |
Subject |
Science |
Chapter |
16 |
Chapter Name |
Light |
NCERT Exemplar Solution Class 8 Science Chapter 16 Light
Multiple Choice Questions
1) Part of the eye which controls the light entering is called
a) Iris
b) Cornea
c) Lens
d) Retina
Answer:- a) Iris
Iris gives the colour to the eyes. These controls the amount of light entering inside the light.
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:- b) Is reflected from the object towards our eye.
Luminous object can emit their own light. But non- luminous object cannot emit light, thus when any light is fall on the object, it reflected towards our eyes and we can see the objects.
3) Light is falling on surface S1, S2, S3, as shown in fig. 16.1.
Fig. 16.1
Surfaces on which the angle of incidence is equal to the angle of reflection is / are
a) S1 only
b) S2 and S3
c) S1 and S2 only
d) All the three surfaces
Answer:- d) All the three surfaces.
All the three surfaces will reflect the light but as regular and irregular or diffused reflection.
4) A tiny mirror M is fixed on w 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 ?
a) A
b) B
c) C
d) D
Answer:- a) A
A should be the position of the eye so that mirror will be visible.
Fig. 16.2
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.
Fig. 16.3
At which point should the eye be placed so that the hole can be seen ?
a) A
b) B
c) C
d) D
Answer:- a) A
At the place of A eyes should be placed to see the hole because angle of incidence will be equal to angle of reflection.
6) Two mirrors A and B are placed at right angles to each other as shown in fig. 16.4.
Fig. 16.4
A ray of light incident on mirror A at an angle of 25° falls on mirror B after reflection. The angle of reflection for the ray reflected from mirror B would be
a) 25°
b) 50°
c) 65°
d) 115°
Answer:- c) 65°
It will fall on the mirror B after reflection of 25° angle therefore it will be of an 65°.
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:- b) Cones are sensitive to bright light.
Cones are sensitive to bright light and rods are sensitive to dim light.
8) In the figure of the human eye (fig. 16.5 ), the cornea is represented by the lette
Fig. 16.5
a) A
b) B
c) C
d) D
Answer:- c) C
represents the Cornea of eye.
Very Short Answer Questions
9) Name the part of the eye which gives colour to the eyes.
Answer:- The part which gives the colour to the eye is Iris. When we found that someone has green, blue, brown, or black is the colour of iris. Iris is the dark muscular structure. These iris perform the function of controlling the amount of light entering the eye.
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:-While waving the hand very fast in air in front of eyes, fingers appear blurred due to the persistence of the vision. The image formed on our retina remain there for about 1/16th of a second. If the moving objects move faster than 16 seconds. Then the persistence of vision occurs.
11) How many times is a ray of light reflected by two plane mirrors placed parallel and facing each other ?
Answer:- Two plane facing each other and placed parallel can reflect the ray of light number of times (infinite).
12) The angle between incident ray and reflected ray is 60°. What is the value of angle of incidence?
Answer:- The value of angle of incidence must be 30°. Because Reflected ray and incident ray combine form the angle of 60°. A normal is there between them and it separate both rays from middle.
13) The distance between the object and it’s image formed by a plane mirror appears to be 24 cm. What is the distance between the mirror and the object?
Answer:-the distance from mirror to the object will be 12 cm. As the distance from the object in appearance (image) and the actual distance is same. Because it was a plane mirror. The object is placed at 12 cm and the image formed at 12 cm total 24 cm distance was appearing in image.
Short Answer Questions
14) What happens to light when it gets dispersed? Give an example.
Answer:- Dispersion of light is the splitting of the light into its several colours. The example of its is rainbow which is a natural phenomena. Rainbow shows dispersion because water and mirror forms a prism. These prism breaks the light into its several colours.
15) 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
Answer:-
Fig. Showing Position of plane mirror
Here, r shows the angle of reflection
And, i shows the angle of incidence.
16) Look at fig. 16.7 can the image of the child in it be obtained on a screen ?
Fig. 16.7
Answer:- No. These image is obtained by using the two plane mirrors. When we cannot see an object directly that time we can use these method. These is obtained when reflected light will reflect again and a image is obtain. here the image of child will not obtained. But only back side of head will obtained in image.
17) Eyes of the nocturnal birds have large cornea and a large pupil. How does this structure help them?
Answer:- Nocturnal birds cannot see in the day but they can see very well in the night. Nocturnal birds have a large cornea and a large pupil these structure helps them to enter the large amount of light in the eyes. Also a large number of rods and small number of cones are present on their retina. Rods are sensitive to dim light. Therefore they can see the objects in the dim light in night.
18) What kind of lens is there in our eyes? Where does it from the image of an object?
Answer:- We human beings have the Convex type of lenses in our eyes. These convex lenses forms an image on the retina. The image formed on the retina remain on it for about 1/16th of s second. Thus we can see the objects clearly.
19) Which part of the eye gets affected if someone is suffering from cataract ? How is it treated ?
Answer:- With increase in the age, the eyesight sometime becomes foggy and eye lenses becomes cloudy. Then the person suffer From cataract. Sometimes there is loss of vision completely. But it is possible to treat it, the old opaque lenses are removed by a small Operation and a artificial lenses are inserted at that place. These is a modern technology which is safe and simple.
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.
Fig. 16.8
a) How many mirrors should he use to see the objects?
Answer:- three mirrors should be used on each of the three corners to see the objects.
b) Indicate the positions of the mirrors in the figure.
Answer:- Figure showing the positions of the mirrors
c) What must be the angle with respect to the incident light at which he should place the mirrors?
Answer:- their should be 45° angle with respect to incident light and mirrors.
d) Indicate the direction of rays in the figure.
Answer:- Fig. Showing direction of rays in the
e) If any of the mirrors is removed, will he be able to see the objects?
Answer:-No. If any one of the mirror will be removed then he will not be able to see the objects.
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).
Fig. 16.9
Answer:- After making necessary corrections in the above figure, the following correct figure is formed.
figure showing the correct ray diagram.
22) Explain the process which enables us to perceive motion in a cartoon film.
Answer:- Cartoon films are not actually a motion film. These are the drawing or photos which are one by one shown like an projection. These is shown as an sequence at 24 pictures per second and found it like moving video.
23) How is the phenomenon of reflection used in making a kaleidoscope? What are the applications of a kaleidoscope?
Answer:- Kaleidoscope is form when number of mirrors are placed at an angle to each other and number of images are formed which forms beautiful patterns. The reflection of light takes place from one mirror to another mirror and we see the number of images formed on it. These kaleidoscope is used by some designers to make wallpapers and some fabric artist for new patterns.
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.
Fig. 16.10
Answer:-
25) Write down the names of parts of the eye in the blank spaces shown in fig. 16.10.
Fig. 16.11
Answer:-
Following are the parts of eyes.
1) Ciliary muscle
2) Iris
3) Lens.
4) Cornea
5) Retina
6) Optic Nerve