Question

During the formation of an image in a telescope under normal adjustment, the eyepiece is adjusted so that the intermediate image lies:

Options

• At the eyepiece's focal length

• At twice the eyepiece's focal length

• At the least distance of distinct vision from the eyepiece

• At the objective's focal length

Answer 1

The objective of focal length $f_o$ focuses the parallel incident beam at a distance $f_o$ from the objective, forming an inverted intermediate image. For normal adjustment, the eyepiece is adjusted so that the intermediate image lies at the eyepiece's focal length, so the refracted rays emerge as a parallel beam and the final image is at infinity.