ow is not uniformly dark all over, the central partmay be black but it will get brighter as we approach theedges. Thus arrange an ordinary gas flame to cast a shadowof a sheet of card some 10cm. square on a paper screen at adistance of say two metres, the flat side of the flame beingparallel to the… … Fig. 6. Join AC, edge, and look at the gas flame through these holes. Through(1) no portion of the gas flame is visible, through (2) part ofthe flame can be seen, whilethrough (3) nearly the whole isvisible. The black portion calledthe umbra receives no light fromthe flame, the lighter part of…
Heat · Light
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