Four lenses of focal length ±15 cm and ± 150 cm are available for making a telescope. To produce the largest magnification, the focal length of the eyepiece should be

Question

Four lenses of focal length ±15 cm and ± 150 cm are available for making a telescope. To produce the largest magnification, the focal length of the eyepiece should be (A) + 15 cm (B) +150 cm (C) -150 cm (D) -15 cm

Tardigrade Admin · Accepted Answer

Magnifying power of telescope, M= fo /fe To produce largest magnifications fo> fe and f0 and fe both should be positive (convex lens) Therefore fe = +15 cm

Q. Four lenses of focal length $\pm$ 15 cm and $\pm$ 150 cm
are available for making a telescope. To produce
the largest magnification, the focal length of the
eyepiece should be

+ 15 cm

+150 cm

-150 cm

-15 cm

Magnifying power of telescope, $M = f_{o} / f_{e}$
To produce largest magnifications $f_{o} > f_{e} an d f_{0}$
and $f_{e}$ both should be positive (convex lens)
Therefore $f_{e} = + 15 c m$

Q. Four lenses of focal length ±15 cm and ± 150 cm are available for making a telescope. To produce the largest magnification, the focal length of the eyepiece should be