Question
An astronomical telescope consists of two thin lenses set 36 cm apart and has a magnifying power of 8 in normal adjustment. Calculate the focal lengths of lenses.
Solution
We are given an astronomical telescope.
distance between lenses = 36 cm
magnifying power = 8
In the normal adjustment, the final image is formed at infinity.
...(i)
and
...(ii)
From equations (i) and (ii), we have
and
where,
fo is the focal length of objective and,
fe is the focal length of eye- piece.
distance between lenses = 36 cm
magnifying power = 8
In the normal adjustment, the final image is formed at infinity.
...(i)
and
...(ii)
From equations (i) and (ii), we have
and
where,
fo is the focal length of objective and,
fe is the focal length of eye- piece.
