Question

Please explain thoroughly and draw diagrams when necessary. I usually rate within 24 hours.

The focal length of your Nikon camera lens is 70 mm. It is used for taking pictures of your friend who is 1.5 m tall. What is your friend's distance from the lens if the image just fills the 24-mm vertical dimension of the film?

Answer 1

here by using

1 /f = 1 / v - 1/u

1 / -70 = 1 / v - 1 / u

1 / u - 1 / 70 = 1 /v

(70 - u) / 70u = 1 / v

v = 70u / (70-u)

then

M = height of image / height of object = v / u

24 / 1500 = 70 u / ( 70 - u )* u

24 ( 70-u) = 70 * 1500

u = -4305 mm

the objecct distance is -4305 mm = -4.305 m