Question

What is the aperture diameter of a $12\mathrm{mm}$focal-length lens set to $\mathrm{f}/4.0?$

Short answer

The Diameter of the aperture is$3\mathrm{mm}$.

Step-by-step solution

Given information

We have given,

f-number = $4$

Focal length = $12\mathrm{mm}$

we have to find the diameter of the aperture.

Simplify

We know that the f-number is defined the ratio between the focal length and diameter.

$$\begin{gathered} \mathrm{f}-\mathrm{number}=\frac{\mathrm{f}}{\mathrm{D}} \\ \mathrm{D}=\frac{\mathrm{f}}{\mathrm{f}-\mathrm{number}}=\frac{12\mathrm{mm}}{4} \\ \mathrm{D}=3\mathrm{mm} \end{gathered}$$