Question

If the radius of curvature of a concave mirror is $36cm$, what is its focal length?

Answer 1

Step 1 - Given data and formula.
The radius of curvature ($R$) of a concave mirror is $36cm$.
The formula to find the focal length is $f=\frac{R}{2}$.

Step 2 - Finding the focal length.
Substitute the value into the formula
$$\begin{gathered} f=\frac{R}{2} \\ f=\frac{36cm}{2} \\ f=18cm \end{gathered}$$

Final answer: Hence, the focal length of the given concave mirror is $18cm$.