QUESTIONS AND PROBLEMS 509 



36. Where is the use of a portable plm 



what way do portable photometers resemble the laboratory type? How 

 do they differ? 



37. What is the standard in the Sharp-Millar pip In what 

 \\ay is tin- standard accurately adjusted? How is brightness or illumination 



ired? How is the candlepower of a lamp measured? How is a 

 balance obtained and read? How may the range of the instrument IK* 

 greatly increased'.' 



38. How is the mean horizontal candlepower of a lamp determined with 

 one photometer setting? How may the candlepower in other zones be 

 measured in a similar manner'.' How does the candlepower in a vertical 

 direction of an incandescent lamp compare with that in the hon 

 direction? 



39. Sketch the Rousseau diagram, showing how the mean spherical 

 candlepower may be determined from the polar distribution diagram. What 

 is meant by "spherical reduction factor?" Of what use is a knowledge 

 of its value? 



40. Why are reflectors useful even although they absorb a considerable 

 amount of light? When may it be desirable to throw light upward'.' Down- 

 ward? How is this accomplished'.' 



41. What are the illuminants most generally used in interior illumina- 

 tion? What important factors must be considered when illuminating an 

 interior'.' 



42. What illumination is required for reading, writ inn When 

 should such illumination be furnished entirely I.-. if By 

 individual desk lamps? 



43. When a room is to IM> illuminated by a single unit how should the 

 reflector differ from those required when a number of units are used? 



44. What is indirect lighting'.' What is its chief advantage? What are 

 its disadvantages? How arc these disadvantages overcome by the use 



.i-indirect fixtures? 



45. Where are individual lamps required in factory illumination 1 .' How 

 do overhead belts and traveling cranes affect the placing of the lighting 

 unit- 



46. In what way does Street illumination differ from interior illumination'.' 

 How do the lighting - compare m the two cases? What can be 



: light in comparing the t 



47. V. uniform street illumination !* objec- 



street lighting of uniform intei. < : \\ hv is its use < I good 



engineering under these cnnditio- 



48. How does the ,-sist in ilium it is meant 



does autoin.il.il.' <( street 



illumination problems'.' l ; lacing of light* on curvea, 



49. Wh:.- by "flood ligl/ 1 where is this type of illumi- 

 nation used? 



