LIGHT AND VISION 159 



30. Why do owls have such large openings in the iris? 



31. Why is one dazzled when brought suddenly from darkness into a 

 brightly lighted room? 



32. Why is it difficult to see when we first go into the dark from a 

 lighted room. 



33. On a dark night, one is able to see fairly well after he has been in 

 the dark for some time. Why? 



34. Why are cameras always painted black inside? 



35. The interior of the ordinary human eye is black but albinos lack 

 this pigment. Albinos cannot see well in bright light. Why? 



36. Hold a pencil a few inches from the eye and look at some point 

 beyond it, first with one eye and then with the other. What advantage 

 is there in judging distances, size, and shape in having two eyes? 



37. Punch a hole in each end of a small card, such as a visiting card, 

 and in each hole tie a piece of twine. Draw a cage on one side of the card 

 and an animal exactly opposite on the other. Revolve the card by means 

 of the twine and explain the effect produced. 



38. How many distinct and consecutive objects can one see in a 

 second? 



