Question

An optical device has been given to a student and he determines its focal length by focusing the web of the sun on a screen placed 24 cm from the device on the same side of the sun. Name the optical device.

Answer 1

The optical device that focuses the sunlight on a screen is a convex lens or converging lens, and its focal length is the distance from the lens to the focused bright spot. The power of the lens can be calculated as the inverse of the focal length in meters.

Step-by-step explanation:

The optical device given to the student, which focuses sunlight onto a screen, is known as a convex lens or a converging lens. This kind of lens has the special ability to focus parallel rays of light coming from a distant object like the Sun. In this case, the rays from the Sun are focused on a screen to form a sharp bright spot, which means the distance from the lens to the screen is equal to the focal length of the lens.

To calculate the power of a convex lens, you would take the inverse of the focal length (in meters). Given that the focal length, in this scenario, is 24 cm or 0.24 meters, the power of the lens would be approximately 1/0.24, which equates to approximately 4.17 diopters (D).

Knowing the focal length and power is crucial for a variety of applications involving lenses, such as designing eyewear, creating photographic equipment, or constructing telescopes and microscopes.