LIGHT, Class 8 Science NCERT Solutions PDF Download

 Page 1


   
 
 
Material downloaded from http://myCBSEguide.com and http://onlineteachers.co.in 
Portal for CBSE Notes, Test Papers, Sample Papers, Tips and Tricks 
 
 
Class–VIII (CHAPTER-16) 
LIGHT 
Answers  
 
1. We cannot see objects in the dark room. But, we can see objects outside the room, in 
case there is a light outside the room. To see an object need light which must reflect 
from the object to the eyes.  
2.  
Regular reflection Diffused reflection 
 The reflected rays are parallel to 
incident rays.  
 It occurs when incident ray falls on 
smooth or polished surface. 
 The reflected rays are not parallel to 
incident rays. 
 It occurs when incident falls on rough 
surface.  
 
No, diffused reflection is not the failure of the laws of reflection. 
3. (a) Regular reflection will occurs because of polished surface. 
(b) Diffused reflection will take place because it is rough surface. 
(c) Diffused reflection will take place because it is not polished surface. 
(d) Diffused reflection will take place because marble and water will form prism. 
(e) Regular reflection takes place because plane mirror is a polished surface. 
(f) Diffused reflection due to rough surface. 
4. The laws of reflection are 
  (a) The angle of incident is equal to angle of reflection. 
(b) The ray of incidence, ray of reflection and normal to the point incidence lie in 
same plane.  
5. Material required:- white sheet of paper, a drawing board, drawing pins, a comb. 
  Procedure:  
(i) A white sheet of paper on a drawing board is fixed. 
(ii) A strip of plane mirror is taken and placed in the path of light ray. 
(iii) The ray of light will be reflected. 
(iv) Angle of incidence and angle of reflection on the sheet of paper is drawn. 
Page 2


   
 
 
Material downloaded from http://myCBSEguide.com and http://onlineteachers.co.in 
Portal for CBSE Notes, Test Papers, Sample Papers, Tips and Tricks 
 
 
Class–VIII (CHAPTER-16) 
LIGHT 
Answers  
 
1. We cannot see objects in the dark room. But, we can see objects outside the room, in 
case there is a light outside the room. To see an object need light which must reflect 
from the object to the eyes.  
2.  
Regular reflection Diffused reflection 
 The reflected rays are parallel to 
incident rays.  
 It occurs when incident ray falls on 
smooth or polished surface. 
 The reflected rays are not parallel to 
incident rays. 
 It occurs when incident falls on rough 
surface.  
 
No, diffused reflection is not the failure of the laws of reflection. 
3. (a) Regular reflection will occurs because of polished surface. 
(b) Diffused reflection will take place because it is rough surface. 
(c) Diffused reflection will take place because it is not polished surface. 
(d) Diffused reflection will take place because marble and water will form prism. 
(e) Regular reflection takes place because plane mirror is a polished surface. 
(f) Diffused reflection due to rough surface. 
4. The laws of reflection are 
  (a) The angle of incident is equal to angle of reflection. 
(b) The ray of incidence, ray of reflection and normal to the point incidence lie in 
same plane.  
5. Material required:- white sheet of paper, a drawing board, drawing pins, a comb. 
  Procedure:  
(i) A white sheet of paper on a drawing board is fixed. 
(ii) A strip of plane mirror is taken and placed in the path of light ray. 
(iii) The ray of light will be reflected. 
(iv) Angle of incidence and angle of reflection on the sheet of paper is drawn. 
   
 
 
Material downloaded from http://myCBSEguide.com and http://onlineteachers.co.in 
Portal for CBSE Notes, Test Papers, Sample Papers, Tips and Tricks 
 
 
(v) The incident and reflected rays along the paper is observed. 
(vi) Now the sheet of paper is bent a little at the position of the reflected ray. 
(vii) Keeping the incident ray and the normal in the plane of the drawing board, 
the reflected ray is tried be seen now. 
Observation:  
 The incidence ray, reflected ray and normal lie in same plane. 
6. Fill in the blanks. 
(a) A person 1 m in front of a plane mirror seems to be 2 m away from this 
image. 
(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. 
(c) The size of the pupil becomes large when you see in dim light. 
(d) Night birds have less cones than rods in their eyes. 
7. (a) always. 
8. (b) Virtual, behind the mirror and of the same size as the object. 
9. Kaleidoscope is an optical instrument used to see a  number of beautiful patterns. It 
is made up of a circular cardboard tube or tube of a thick chart paper in which 
rectangular mirror strips are joined together to form a prism. At one end of tube, 
touching these mirrors, a circular glass plate is fixed. Several small pieces of 
coloured glass are placed upon it. This end is closed by ground glass plate and 
beautiful patterns are seen through the other end of the kaleidoscope.  
 
10. 
    
11. Laser torch can harm or even damage eye. So. Her teacher advised her not to do so.   
12. The following care should be taken to keep our eyes healthy: 
 (a) We should not look at the sun or a powerful light source diretly. 
Page 3


   
 
 
Material downloaded from http://myCBSEguide.com and http://onlineteachers.co.in 
Portal for CBSE Notes, Test Papers, Sample Papers, Tips and Tricks 
 
 
Class–VIII (CHAPTER-16) 
LIGHT 
Answers  
 
1. We cannot see objects in the dark room. But, we can see objects outside the room, in 
case there is a light outside the room. To see an object need light which must reflect 
from the object to the eyes.  
2.  
Regular reflection Diffused reflection 
 The reflected rays are parallel to 
incident rays.  
 It occurs when incident ray falls on 
smooth or polished surface. 
 The reflected rays are not parallel to 
incident rays. 
 It occurs when incident falls on rough 
surface.  
 
No, diffused reflection is not the failure of the laws of reflection. 
3. (a) Regular reflection will occurs because of polished surface. 
(b) Diffused reflection will take place because it is rough surface. 
(c) Diffused reflection will take place because it is not polished surface. 
(d) Diffused reflection will take place because marble and water will form prism. 
(e) Regular reflection takes place because plane mirror is a polished surface. 
(f) Diffused reflection due to rough surface. 
4. The laws of reflection are 
  (a) The angle of incident is equal to angle of reflection. 
(b) The ray of incidence, ray of reflection and normal to the point incidence lie in 
same plane.  
5. Material required:- white sheet of paper, a drawing board, drawing pins, a comb. 
  Procedure:  
(i) A white sheet of paper on a drawing board is fixed. 
(ii) A strip of plane mirror is taken and placed in the path of light ray. 
(iii) The ray of light will be reflected. 
(iv) Angle of incidence and angle of reflection on the sheet of paper is drawn. 
   
 
 
Material downloaded from http://myCBSEguide.com and http://onlineteachers.co.in 
Portal for CBSE Notes, Test Papers, Sample Papers, Tips and Tricks 
 
 
(v) The incident and reflected rays along the paper is observed. 
(vi) Now the sheet of paper is bent a little at the position of the reflected ray. 
(vii) Keeping the incident ray and the normal in the plane of the drawing board, 
the reflected ray is tried be seen now. 
Observation:  
 The incidence ray, reflected ray and normal lie in same plane. 
6. Fill in the blanks. 
(a) A person 1 m in front of a plane mirror seems to be 2 m away from this 
image. 
(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. 
(c) The size of the pupil becomes large when you see in dim light. 
(d) Night birds have less cones than rods in their eyes. 
7. (a) always. 
8. (b) Virtual, behind the mirror and of the same size as the object. 
9. Kaleidoscope is an optical instrument used to see a  number of beautiful patterns. It 
is made up of a circular cardboard tube or tube of a thick chart paper in which 
rectangular mirror strips are joined together to form a prism. At one end of tube, 
touching these mirrors, a circular glass plate is fixed. Several small pieces of 
coloured glass are placed upon it. This end is closed by ground glass plate and 
beautiful patterns are seen through the other end of the kaleidoscope.  
 
10. 
    
11. Laser torch can harm or even damage eye. So. Her teacher advised her not to do so.   
12. The following care should be taken to keep our eyes healthy: 
 (a) We should not look at the sun or a powerful light source diretly. 
   
 
 
Material downloaded from http://myCBSEguide.com and http://onlineteachers.co.in 
Portal for CBSE Notes, Test Papers, Sample Papers, Tips and Tricks 
 
 
 (b) Too light or too much light is bad for the eyes. 
(c) If advised, suitable spectacles should be used. 
(d) We should always read from a normal distance for distinct vision. 
(e) We should never rub our eyes if any small particle or dust goes into the eyes. 
(f) Food containing Vitamin A should be used. 
13. The angle of incidence is 45
0
. 
14. Infinite number of images of the candle will be formed, if it is placed between two 
parallel plane mirrors.  
15. 
  
16. Boojho will not be able see himself in the mirror. But he can see image of objects 
situated at P and Q.  
17. (a) A image will be formed at the same distance behind the mirror. 
 (b) Yes. 
 (c) Yes. 
 (d) The image remains at the same place. The image moves only if the object or the 
mirror is moved.