Question

A lens with a focal length of 25 cm is placed 40 cm in front of a lens with a focal length of 5.0 cm. How far from the second lens is the final image of an object infinitely far from the first lens? express your answer using two significant figures.

Answer 1

When an object is placed infinitely far from a converging lens, the resulting image will be formed at the focal point of the lens. In this case, the first lens has a focal length of 25 cm, so the image of the object formed by the first lens will be 25 cm behind it. Then, the second lens with a focal length of 5 cm will create a new image by converging the light rays from the first image. The distance from the second lens to the final image can be found using the lens equation: 1/f = 1/do + 1/di.

Step-by-step explanation:

When an object is placed infinitely far from a converging lens, the resulting image will be formed at the focal point of the lens.

In this case, the first lens has a focal length of 25 cm, so the image of the object formed by the first lens will be 25 cm behind it.

Then, the second lens with a focal length of 5 cm will create a new image by converging the light rays from the first image. The distance from the second lens to the final image can be found using the lens equation: 1/f = 1/do + 1/di.

Let's assume the final image distance as di. We know that the object distance, do, is infinity. Plugging these values into the lens equation, we get 1/5 = 0 + 1/di. Solving for di, we find that the final image is located at di = 5 cm behind the second lens.