Question

The optical instrument with zero power is:
(A) microscope
(B) telescope
(C) eyepiece
(D) all of the above

Answer 1

Hint
The power and the focal length both are inversely proportional, so the lens which have the high focal length which have the very minimum power, because both are inversely proportional to each other. The zero-power lenses are used to see long-range objects.

Complete step by step answer
The zero-power lens is used to see the long-range object and also used for other applications such as when you are working in the computers, the zero-power lens which protects the rays from the monitor to enter the eyes. The relation between the power of the lens and the focal length is given by, $P = \dfrac{1}{f}$, where $P$ is the power of the lens and $f$ is the focal length of the lens. As we want to minimize the power of the lens, so that the focal length has to be increased.
From the options which are given in the question, the telescope is the only lens which has a high focal length, so that the power of the telescope is very close to zero and approximately the power of the telescope is said to be zero. The reason for the telescope having no power is that the telescope is designed to see the long distance so that the main target is to increase the focal length, so that the power of the lens is not to be maintained and reduced, the power of the lens to zero.
Hence, the option (B) is the correct answer.

Note
Usually, the telescope reduces the power and brings the focus, and increases the aperture so the image is more clear and brighter. The magnification of the telescope is to enlarge the image depending on the combination of the lenses used in the telescope. The eyepiece in the telescope which performs the magnification process.