What is the magnification of an astronomical telescope whose objective lens has a focal length of 74 cm and whose eyepiece has a focal length of 2.4 cm ? Follow the sign conventions.

The magnification of an astronomical telescope is -30.83.

Explanation:

The expression for the magnification of an astronomical telescope is as follows;

Here, M is the magnification of an astronomical telescope, is the focal length of the eyepiece lens and is the focal length of the objective lens.

It is given in the problem that an astronomical telescope having a focal length of objective lens 74 cm and whose eyepiece has a focal length of 2.4 cm.

Put and in the above expression.

M=-30.83

Therefore, the magnification of an astronomical telescope is -30.83.

t = 1/400 h   ⇔ 0.0025 h ⇔ 9s ⇔ 0.15 m

any of the answers are correct.