The focal length is denoted by the letter

Finally, the distance from the mirror to the focal point is known as the focal length (abbreviated by "f").

1. What is the unit of focal length?
2. Is focal length always r 2?
3. Why is focal length r 2?
4. What is the length f?

What is the unit of focal length?

Focal length is measured in metres. Metre(m) is the unit which is used to measure the length or distance. Therefore, option (C) is the correct answer.

Is focal length always r 2?

The relation between focal length (f) and radius of curvature (R) of a spherical mirror is that the focal length is equal to half of the radius of curvature i.e. f=R2.

Why is focal length r 2?

Radius of curvature is observed to be equal to twice the focal length for spherical mirrors with small apertures. Hence R = 2f . We can say clearly that the principal focus of a spherical mirror lies at the centre between the centre of curvature and the pole. Read more about Electricity and magnetism.

What is the length f?

Focal length f is the distance of principal focus from the pole of mirror.