Light year is a unit of measurement of

The focal length of the objective lens of a telescope is 50 cm. If the magnification of the telescope is 25, then the focal length of the eyepiece is

Which one of the following force is non-central and non-conservative?

Consider the following statements relating to Richter scale.

1. It was devised in 1935 by Charles F. Richter.

2. It describes the quantity of energy released by a single earthquake.

3. Richter scale has no upper limit.

Which of the statement(s) given above is/are correct?