How do you determine the focal length of a lens?

To determine the focal length of a lens, you can use the lens equation.

The focal length of a lens is the distance from the lens to the point where parallel rays of light converge after passing through the lens. The lens equation relates the focal length of a lens to the distance of an object from the lens and the distance of the image from the lens.

The lens equation is 1/f = 1/o + 1/i, where f is the focal length of the lens, o is the distance of the object from the lens, and i is the distance of the image from the lens. To use this equation, you need to measure the distance of the object from the lens and the distance of the image from the lens. The distance of the object can be measured using a ruler or tape measure, and the distance of the image can be measured using a screen or a piece of paper.

Once you have measured the distances, you can plug them into the lens equation and solve for the focal length of the lens. It is important to note that the units of measurement for the distances must be consistent, for example, if the distance of the object is measured in metres, then the distance of the image should also be measured in metres.

In summary, the focal length of a lens can be determined using the lens equation, which relates the focal length of the lens to the distance of the object from the lens and the distance of the image from the lens. To use this equation, you need to measure the distances of the object and the image and plug them into the equation.