13.(Pg. [159]) Upon what does the intensity of a shadow depend?
14.(Pg. [159]) How are shadows affected by the size of the luminous body, as represented in [plate 15, fig. 3]?
15.(Pg. [159]) When is the shadow larger than the intercepting body?
16.(Pg. [160]) What is explained by [fig. 4, plate 15]?
17.(Pg. [160]) What will be the effect of several lights, as in [fig. 5, plate 15]?
18.(Pg. [160]) Why will neither of these shadows be very dark?
19.(Pg. [160]) What becomes of the light which falls upon an opaque body?
20.(Pg. [160]) What is meant by reflection?
21.(Pg. [161]) What is meant by the incident, and reflected rays?
22.(Pg. [161]) What is the result, when the incident ray falls perpendicularly, and what, when it falls obliquely?