Question

The radius of curvature of a spherical mirror is $90cm$, what is its focal length?

Answer 1

Step 1 - Given data and formula.

The radius of the spherical mirror is $R=90cm$
The formula for the focal length is $f=\frac{R}{2}$

Step 2 - Finding the focal length.

Substitute the value of $R$ into the formula to calculate the focal length.
$$\begin{gathered} f=\frac{R}{2} \\ f=\frac{90cm}{2} \\ f=45cm \end{gathered}$$

Final answer - Hence, the focal length of a spherical mirror is $45cm$.