A camera is used to photograph the full moon, which has an angular diameter of 0.51. The image on the film is 2.5 mm in diameter. What is the focal length of the lens?
a. 6.3 mm
c. 13 mm
b. 280 mm
d. 450 mm
Question 2
A camera has a lens of focal length 50 mm and an f-number of 4.0 . What is the diameter of the lens?
a. 50 mm
c. 25 mm
b. 100 mm
d. 13 mm