158 HOW WE USE LIGHT 



1. Light travels with greater speed than anything else. 



2. Light travels in straight lines. 



3. Light rays may be bent by reflection or by refraction. 



4. Light produces chemical changes of much value to man. 



Before making your review summary, test your knowledge of 

 the facts of the unit by checking over the text so as to be sure you 

 know the facts underlying the generalizations. Then, using the 

 generalizations, the material in the text, and everything you have 

 read, seen, or done yourself, make a summary outline for your 

 notebook. This outline you may use when you make a recitation. 



TEST ON FUNDAMENTAL CONCEPTS 



Make two vertical columns in your workbook. Head one CORRECT 

 and the other INCORRECT. Under the first place the numbers of all state- 

 ments you believe to be correct. Under the second place all the numbers 

 of the statements you believe to be incorrect. Your grade = right 

 answers X 2^. 



I. Light travels : (1) in straight lines ; (2) through translucent 

 bodies; (3) 1100 feet per second; (4) more slowly through water 

 than through air. 



II. A real image may be produced: (5) by a plane mirror; 

 (6) by a piece of plate glass; (7) by a pinhole camera; (8) by a 

 concave mirror. 



III. A beam of light will be bent (refracted) when it goes from : 

 (9) air into glass at a 90 angle to the surface ; (10) air to glass at a 

 30 angle; (11) water into air at right angles to the surface; 

 (12) water into air at an angle of 60 between the ray and the 

 surface of the water. 



IV. The ordinary camera lens produces a real image on the film 

 because the lens : (13) reflects the light from the object; (14) re- 

 fracts the light coming into it; (15) sifts or filters out the objec- 

 tionable rays of light which would mar the image; (16) permits 

 light from the object to reach the film. 



V. When a beam of light from candle flame comes to a piece of 

 plate glass at right angles to the surface, some of the light : (17) is 

 refracted; (18) is reflected; (19) is changed to a gas; (20) is 

 transmitted. 



VI. The image of an object in a plane mirror is : (21) larger 

 than the object ; (22) unreal ; (23) the same distance back of the 

 mirror that the object is in front of the mirror; (24) inverted. 



VII. Concave mirrors: (25) may produce real images; (26) 

 are used in some telescopes ; (27) are used in cameras ; (28) are 

 used in automobiles to watch traffic in the rear. 



