Optics Question 481

Question: A movie projector forms an image 3.5m long of an object 35 mm. Supposing there is negligible absorption of light by aperture then illuminance on slide and screen will be in the ratio of

[CPMT 1982]

Options:

A) 100 : 1

B) 104 : 1

C) 1 : 100

D) 1 : 104

Show Answer

Answer:

Correct Answer: B

Solution:

I1r2 so, Illuminance on slide Illuminance on screen=(Length of image on screen)2(Length of object on slide)2

=(3.5 m35 mm)2=104:1



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