Question

Some telephoto cameras use a mirror rather than a lens. What radius of curvature mirror is needed to replace an 800 mm focal length telephoto lens?

a) 400 mm
b) 800 mm
c) 1600 mm
d) 3200 mm

Answer 1

To replace an 800 mm focal length telephoto lens, a mirror with a radius of curvature of 1600 mm is needed, as the radius is twice the focal length of the mirror.

Step-by-step explanation:

In optics, to determine the necessary radius of curvature for a mirror to replace a telephoto lens with a certain focal length, we use the mirror equation which relates the focal length (f) of a mirror to its radius of curvature (R) through the equation f = R/2. For a telephoto lens with an 800 mm focal length, a mirror must have a radius of curvature that is twice the focal length to achieve the same effect.

Thus, the required radius of curvature would be 1600 mm because 2 times 800 mm equals 1600 mm. Therefore, option (c) 1600 mm is the correct answer to replace an 800 mm focal length telephoto lens with a mirror.