A camera fitted with a lens of focal length 50 mm is being used to photograph a flower that is 5 cm in diameter. The flower is placed 20 cm in front of the camera lens.
(a) At what distance from the film should the lens be adjusted to obtain a sharp image of the flower?
(b) What would be the diameter of the image of the flower on the film?
(c) What is the nature of camera lens?
(a) u = -20 cm = -200 mm
f = 50 mm
\(\frac{1}{v}\) - \(\frac{1}{u}\) = \(\frac{1}{f}\)
\(\frac{1}{v}\) - \(\frac{1}{-200}\) = \(\frac{1}{50}\)
\(\frac{1}{v}\) = \(\frac{1}{50}\) - \(\frac{1}{200}\)
\(\frac{1}{v}\) = \(\frac{3}{200}\)
v = 66.6 mm = 6.66 cm
The film should be at a distance of 6.66 cm behind the camera lens.
(b) d1 = 5 cm = 50 mm
m = \(\frac{v}{u}\) = \(\frac{d_2}{d_1}\)
\(\frac{66.6}{-200}\) = \(\frac{d_2}{50}\)
d2 = 16.65 mm = 1.66 cm
(c) It is a convex lens.