Question

Changing the f-number of a camera lens by 4X will change the light intensity admitted to the film by what factor? A) 16 B) 0.0625 C) 2 D) 0.25 E) 4

Answer 1

Answer:

option B is correct

factor is 0.0625

Explanation:

Given data

camera lens = 4X

to find out

find factor

solution

we know Inverse square law that is the intensity is inversely proportional to the square of the distance from the source i.e f

so we say intensity ( I )  ∝ 1 / f

so I1 / I2 = f2² / f1²

so I2 will be

I2 =   f2² / f1² × I1

I2 =  1 / 4² × I1

I2 = 0.0625

so option B is correct

factor is 0.0625