The power of a lens is a measure of its ability to bend or refract light rays. It is typically measured in units called diopters (D) and is denoted by the symbol “P.”
The power of a lens is determined by its focal length, which is the distance from the lens to the point at which parallel rays of light converge (for a converging lens) or appear to diverge from (for a diverging lens).
Here’s how to calculate the power of a lens:
Converging Lens (Convex Lens):
The power of a converging lens is positive.
It is calculated using the formula:
P = 1 / f
Where:
P is the power of the lens in diopters (D).
f is the focal length of the lens in meters (m). If the focal length is given in centimeters (cm), it should be converted to meters by dividing by 100.
Diverging Lens (Concave Lens):
The power of a diverging lens is negative.
It is also calculated using the formula:
P = 1 / f
The only difference is that the focal length (f) of a diverging lens is considered negative because the focal point is on the same side as the incoming light.
The greater the power of a lens, the stronger its ability to bend light. Converging lenses have positive powers, and they focus light to a point, while diverging lenses have negative powers and cause light to appear to diverge from a virtual focal point.
The power of a lens is an important parameter in optics and is used in various applications, including eyeglasses and contact lenses. Eyeglass prescriptions often specify the power of the lens needed to correct vision problems, such as nearsightedness (myopia) or farsightedness (hyperopia).