IN POPULAR PHYSICS. 49 



50. If yon sit where you can not see another person's 

 image, why can not that person see yours ? 



The angle of incidence is equal to the angle of reflection 

 under all circumstances. If a ray from the other person is not 

 reflected at the right angle to reach your eye, then a ray from 

 you is not reflected at the right angle to reach the other per- 

 son's eye. 



51. IVliy can we see the multiple images in a mirror 

 better if we look into it very obliquely ? 



More light is then reflected to the eye. The ratio of the 

 light reflected to the light refracted increases with the angle of 

 incidence. 



52. Why is an image seen in water inverted ? 



(Examine Fig. 139 in Physics.) 



53. Why is the sun's light fainter at sunset than at 

 midday ? 



(See Physics, p. 191, note.) 



54. WJty can we not see the fence-posts ^vhen we are 

 riding rapidly ? 



Because the images of a succession of objects are formed 

 on the retina at intervals less than that of the duration of a 

 retinal impression. Hence, they all become confused, and noth- 

 ing is seen distinctly. 



55. Ought a red flower to be placed in a bouquet by an 

 orange one ? A pink or blue with a violet one ? 



(Seo Physics, p. 217.) 



These are not complementary colors, and hence do not 

 strengthen each other by contrast. 



56. IVJiy are the clouds ^vhite while the clear sky is 

 blue? 



Prof. Tyndall has shown that the larger particles of vapor 

 scatter light of all colors, i.e., white light; while the smallest 

 particles, only the blue rays. In accordance with this fact, the 

 clouds are white and the sky is blue. If the air were abso- 

 lutely pure, free from all foreign matter, and highly rarefied, 



