Question

What is the$f-number$of a lens with a $35mm$focal length and a$7.0mm$diameter aperture?

Short answer

The value of $f_{number}$is $5.0mm$.

Step-by-step solution

Given information

We have given,

Focal length = $35mm$

Diameter of aperture = $7mm$

we have to find the $f_{number}$of the lens.

Simplify

The$f_{number}$is defined as the ratio between the focal length role="math" localid="1649843050408" $35mm$and the diameter of the aperture is role="math" localid="1649843057651" $7mm$.

$f_{number}=\frac{f}{D}$

role="math" localid="1649843089488" $f_{number}=\frac{35mm}{7mm}$

$f_{number}=5mm$