An astronomical telescope has angular magnification of magnitude 5 for distant objects. The separation between the objective and the eyepiece is 36 cm and the final image is formed at infinity. The focal lengths of the objective and eyepiece are:
Options

Question

An astronomical telescope has angular magnification of magnitude 5 for distant objects. The separation between the objective and the eyepiece is 36 cm and the final image is formed at infinity. The focal lengths of the objective and eyepiece are:

Options

G1 Physics · Accepted Answer

For normal adjustment of the ordinary astronomical telescope, |M| = fₒ/fₑ = 5 and L = fₒ + fₑ = 36 cm. Hence fₒ = 5fₑ and 6fₑ = 36, giving fₑ = 6 cm and fₒ = 30 cm. Therefore option D is correct.