IN PHYSICS. 2 1 9 



46. Why does a bright light, in the night, seem so much 

 nearer than it is ? 



We judge of the distance of an object by its magni- 

 tude, by its distinctness of outline, and by the size, etc., 

 of intervening objects with which we compare it. In the 

 night, the brightness of a light confuses us by its vivid- 

 ness, seeming to be near at hand. Moreover, we cannot 

 see the neighboring objects, whose distance we know o r 

 could estimate in the daylight. Our error is therefore 

 one of judgment. A firo at night thus seems near at 

 hand, and persons often run toward it for great distances, 

 expecting every moment to reach it. 



(See Question 54.) 



48, 49. (See Key, p. 40 ; Questions 47, 48.) 



50. Why is the lens of a fish's eye (seen in the eye-socket 

 of a boiled fish) so convex ? 



The difference of density between the water and the 

 eye is not so great as that between the air and the eye. 

 Hence, to refract the light sufficiently to bring it to a 

 focus on the retina requires a more convex lens. 



(See Dudgeon, on the Human Eye ; and Physics, p. 268, note.) 



51. When do the eyes of a portrait seem to follow a 

 spectator to all parts of a room ? 



This is noticed only in a full-face portrait. In that 

 case the spectator, when he goes to either side, fails to 

 see the side of the eyeballs, and hence the effect is that 

 of looking directly into the eye. " A rifleman, portrayed 

 as if taking aim directly in front of the picture, appears 

 to every observer to be pointing at him specially." 



5 2 . Why does the dome cf ike sky seem flattened ? 



