Reflection of Light — Question 1

Focal length = $\dfrac{1}{2}$ x Radius of curvature

Given,

R = 40 cm

Substituting the values in the formula above we get,

$\text{Focal length} = \dfrac{1}{2} \times 40 \\[0.5em] \text{Focal length} = 20 \text{ cm}$

Hence, focal length of the convex mirror = 20 cm.