NCERT Solutions Class 8 Science Chapter 16 Light
NCERT Solutions Class 8 Science Chapter 16 Light: National Council of Educational Research and Training Class 8 Science Chapter 16 Solutions – Light. NCERT Solutions Class 8 Science Chapter 16 PDF Download.
NCERT Solutions Class 8 Science Chapter 16: Overview
|
Board |
NCERT |
| Class |
8 |
|
Subject |
Science |
| Chapter |
16 |
|
Chapter Name |
Light |
| Topic |
Exercise Solutions |
NCERT Solutions Class 8 Science Chapter 16 – Light
CHAPTER: – 16 (Light)
Exercise: –
1)Suppose you are in a dark room. Can you see objects in the room? Can you see objects outside the room? Explain.
Ans: – There will be no visibility in a dark room as there is no light is present. So, we couldn’t see any object because of the reflection from the object. In general, what we are see in a daytime is nothing but the reflection of the light from each object.
2)Differentiate between regular and diffused reflection. Does diffused reflection mean the failure of the laws of reflection?
Ans: –
| Regular reflection |
Diffused reflection |
| Surface are shiny and smooth. | Surface is unpolished. |
| Rays are parallel after reflection. | Rays are not parallel after reflection. |
| The reflected object seen as properly. | Whereas the reflected object is not seen properly. |
The failure of laws of reflection doesn’t mean that the diffused reflection it may be because of the unpolished surface like cardboard.
3)Mention against each of the following whether regular or diffused reflection will take place when a beam of light strikes. Justify your answer in each case.
(a) Polished wooden table
Ans: – Because of the polished wooden table surface regular reflection will takes place.
(b) Chalk powder.
Ans: – Because of the rough surface of chalk there will be diffused reflection.
(c) Cardboard surface.
Ans: – Cardboard surface is rough so there will be diffused reflection.
(d) Marble floor with water spread over it.
Ans: – As in marble floor with water spread makes the surface shiny and smooth as well so there will be regular reflection.
(e) Mirror
Ans: – As the surface of the mirror is smooth and shiny there will be regular reflection seen.
(f) Piece of paper.
Ans: – Because of the rough surface in the paper there will be diffused reflection happened.
4)State the laws of reflection.
Ans: – The laws of reflection are
- The angle of reflection is always equal to the incidence angle.
- The incidence rays, normal line and reflected rays will meet at same plane.
5) Describe an activity to show that the incident ray, the reflected ray and the normal at the point of incidence lie in the same plane.
Ans: –
6)Fill in the blanks in the following.
(a) A person 1 m in front of a plane mirror seems to be ____2_____ m away from his image.
Explanation- (R=f/2)
(b) If you touch your _____left_______ ear with right hand in front of a plane mirror it will be seen in the mirror that your right ear is touched with ____left hand____.
Explanation- (As mirror always reflected a inverted image)
(c) The size of the pupil becomes ____large________ when you see in dim light
Explanation- (As it focusses on the object)
(d) Night birds have ___lesser_________ cones than rods in their eyes.
Explanation- (The species which is able to see in night must have small number of cones cell in eyes)
Choose the correct option in Questions 7 – 8
7)Angle of incidence is equal to the angle of reflection.
(a) Always (b) Sometimes
(c) Under special conditions (d) Never.
Ans: – Option(a).
Explanation- (According to laws of reflection)
8)Image formed by a plane mirror is
(a) virtual, behind the mirror and enlarged.
(b) virtual, behind the mirror and of the same size as the object.
(c) real at the surface of the mirror and enlarged.
(d) real, behind the mirror and of the same size as the object.
Ans: – Option(b).
Explanation- (Its characteristics of plane mirror)
9)Describe the construction of a kaleidoscope.
Ans: – A Kaleidoscope used as the optical instrument which made up with the cardboard tube. The rectangular stripes or mirror is joined together to forms this tube. One end of the tube is attached by the coloured glass and other with the ground glass and makes it.
10) Draw a labelled sketch of the human eye.
Ans: –
11) Gurmit wanted to perform Activity 16.8 using a laser torch. Her teacher advised her not to do so. Can you explain the basis of the teachers advise?
Ans: – Gurmit wanted to perform the activity by using the lesser torches but which is more dangerous as this will made someone completely blind. So, he should avoid these steps. The high intensity of light always creates an affect in our eyes.
12) Explain how you can take care of your eyes.
Ans: – Eyes is very sensitive things which we should take care by various ways like wash our eyes at first morning with fresh water, and do repeatedly when we came back from outside as well. We should avoid to focus in low light as well as high powered light.
13) What is the angle of incidence of a ray if the reflected ray is at an angle of 90° to the incident ray?
Ans: –
14)How many images of a candle will be formed if it is placed between two parallel plane mirrors separated by 40 cm?
Ans: – As we all know that there will be formed infinite number of images in between two parallel plane mirrors. So, this will be not counted or not possible. There forms a infinite number of images between these two parallel plane which we see in various places like saloon when two mirror is face to face.
15) Two mirrors meet at right angles. A ray of light is incident on one at an angle of 30° as shown in Fig. 16.19. Draw the reflected ray from the second mirror.
Ans: –
16) Boojho stands at A just on the side of a plane mirror as shown in Fig.16.20. Can he see himself in the mirror? Also, can he see the image of objects situated at P, Q and R?
Ans: –
17)(a) Find out the position of the image of an object situated at A in the plane mirror (Fig. 16.21).
(b) Can Paheli at B see this image?
(c) Can Boojho at C see this image?
(d) When Paheli moves from B to C, where does the image of A move?
Ans: –
