Ray Optics and Optical Instruments - Result Question 35
35. A lens having focal length and aperture of diameter forms an image of intensity . Aperture of diameter in central region of lens is covered by a black paper. Focal length of lens and intensity of image now will be respectively:
[2010]
(a)
(b)
(c)
(d)
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Answer:
Correct Answer: 35. (c)
Solution:
- (c) By covering aperture, focal length does not change. But intensity is reduced by
times, as aperture diameter is covered.