International Library of Technology · Scranton, International Textbook Co. · leaf 213
illumination on the area abed will be a certain amount.Now, suppose the screen to be moved back to the position C,4 feet from A. The total amount of lisfht that fell on the 16 ELECTRIC LIGHTING. 15 area a b c d will now be distributed over the area a b c[ d.The area a! b c d is four times that of a… … Fig. 10. follows that the light per unit area or .the intensity of illumi-nation on a b c d is only one-quarter that on a b c d. Inother words, doubling the distance of the screen from thesource has cut down the intensity of illumination to one-fourth its former value. If the distance A m were…
Electrical engineering
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