Phillips, Percy · London : T. C. & E. C. Jack ; New York : Dodge Pub. Co. · leaf 64
ch element is halved theillumination at P will be half that if the obstacle wereabsent, i.e. quarter that due to the first zone. For apoint Q the point C will be the centre of the zones,and there will be a complete half of the system ofzones above C. Below C we shall have in additionthe other half… … 62 THE SCIENCE OF LIGHT will therefore be three-quarters that due to the firstzone, or three times as much as at P. Now suppose CEis the width of two zones, then the illumination at Qwill be due to half of the whole system plus half of thefirst two zones. The first two zones practically…
Light
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