A camera is supplied with two interchangeable lenses whose f

A camera is supplied with two interchangeable lenses, whose focal lengths are 21.0 and 150.0 mm. A woman whose height is 1.70 m stands 8.60 m in front of the camera. What is the height (including sign) of her image on the image sensor, as produced by (a) the 21.0-mm lens and (b) the 150.0-mm lens?

Solution

1/f = 1/di + 1/do, Magnification = -di/do = hi/ho

for a)
f = .0210 m , h(object) = 1.70 m , do= 8.60 m

1/.0210 m = 1/8.60 m + 1/di

di = .0211 m

M= -.0211 m/8.60m = h(image)/1.70 m

hi = -.0004171 m

for b)
f = .1500 m , do = 8.60 m , ho=1.70 m

1/.1500 m = 1/ 8.60m + 1/di

di = .1527 m

M = -.1527m/8.60m = hi/1.70m

hi= -.030185