Question

A camera takes a properly exposed photo with a 4.0 mm diameter aperture and a shutter speed of 1/1000 s. If the photographer focuses on the same point, but changes the speed to 1/250 s. What needs to happen to the diameter of the aperture, if it is still properly exposed?a. Nothing b. D' = 16 mm c. D'=1.0 mm d. D' = 8.0 mm e. D'=2.0 mm

Answer 1

Answer:

option E

Explanation:

given,

diameter = 4 mm

shutter speed = 1/1000 s

diameter of aperture = ?

shutter speed = 1/250 s

exposure time to the shutter time

$E V = log_2(\dfrac{N^2}{t})$

N is the diameter of the aperture and t is the time of exposure

now,

$log_2(\dfrac{N^2}{t_1})=log_2(\dfrac{N^2}{t_2})$

$\dfrac{N_1^2}{t_1}=\dfrac{N_2^2}{t_2}$

inserting all the values

$\dfrac{4^2}{1000}=\dfrac{N_2^2}{250}$

      N₂² = 4

      N₂ = 2 mm

hence , the correct answer is option E