The unit of power of a lens is:

• A. meter
• B. dyne
• C. dioptre
• D. newton

The unit of power of a lens is known as the dioptre. This measurement indicates how strongly a lens converges or diverges light. The formula for calculating the power (P) of a lens is:

Understanding Dioptres

A lens with a power of 1 dioptre has a focal length of 1 meter. The formula can be expressed as:

• P = 1/f, where P is the power in dioptres and f is the focal length in meters.

Other Units Explained

To clarify the other options:

• Meter: A unit of length, not related to lens power.
• Dyne: A unit of force in the CGS system.
• Newton: A unit of force in the SI system.

In summary, the correct answer is C. dioptre.