Question

Find the focal length of a concave mirror whose radius of curvature is 38 cm.

Answer 1

R=38cm
R=f/2
f=2R
therefore
f=2×38
f=76cm

Answer 2

This can be solved using the formula R = 2f

R = 38 cm

f = $\frac{R}{2}$

f = $\frac{38}{2}$

∴f = 19 cm

This gives the answer, the focal length of the mirror is 19cm.