Ray optics , optical instruments

Question

The focal lengths of objective and eyepiece of a telescope are 200 cm and 10 cm, respectively. It is used to get an image of the sun on a screen placed 40 cm behind the eyepiece. The diameter of the image is 6 cm. What is the diameter of the sun? Take, the distance from earth to the sun is 15 x 10¹¹ m.

Answer 1

For eyepiece (from diagram),

\(\frac{A.B.}{A.O_2} = \frac{A..B..}{A..O_2}\)

A.B.= radius of intermediate image