Question

University Physics Ch. 31 #84

You're given two two lenses with two different diameters, Knowing nothing, you can conclude that

a. the larger lens is faster

b. the smaller lens has a shorter focal length

c. the smaller lens suffers less spherical aberration (?)

d. none of the above

Answer 1

ANSWER - : A,B,C

A lens with a larger maximum aperture is called a "fast lens" because it delivers more light intensity to the focal plane, achieving the same exposure with a faster shutter speed . HENCE THE LARGER DIAMETER LENS WILL BE A FASTER LENS -----> OPTION A

f = R/2   or D/4

HENCE , smaller lens has a shorter focal length DUE TO SMALL DIAMETER ----->OPTION B

The spherical aberration effect is proportional to the fourth power of the diameter and inversely proportional to the third power of the focal length, so it is much more pronounced at short focal ratios,

so , spherical aberration is proportional to D^4

hence , smaller lens will suffer less spherical aberration

OPTION -: C