An astronomical telescope has objective and eyepiece of focal lengths 40cm and 4cm respectively. To view an object 200cm away from the objective, at what distance the lenses must be separated (in cm )?

Question

An astronomical telescope has objective and eyepiece of focal lengths 40cm and 4cm respectively. To view an object 200cm away from the objective, at what distance the lenses must be separated (in cm )? (A)  (B)  (C)  (D)

Tardigrade Admin · Accepted Answer

(1/V)-(1/- 200)=(1/40) (1/V)=(5/5)(1/40)-(1/200) =(5/200)-(1/200) <img class="img-fluid question-image" alt="Solution" src="https://cdn.tardigrade.in/q/nta/p-dk2c4k7ywlgp1lz7.jpg" /> (1/V)=(4/200)=(1/50) V=50 ∴ d=50+4=54 cm

Q. An astronomical telescope has objective and eyepiece of focal lengths $40 c m$ and $4 c m$ respectively. To view an object $200 c m$ away from the objective, at what distance the lenses must be separated (in $c m$ )?

$\frac{1}{V} - \frac{1}{- 200} = \frac{1}{40}$
$\frac{1}{V} = \frac{5}{5} \frac{1}{40} - \frac{1}{200}$
$= \frac{5}{200} - \frac{1}{200}$

$\frac{1}{V} = \frac{4}{200} = \frac{1}{50}$
$V = 50$
$∴ d = 50 + 4 = 54 c m$

Q. An astronomical telescope has objective and eyepiece of focal lengths 40cm and 4cm respectively. To view an object 200cm away from the objective, at what distance the lenses must be separated (in cm )?

V1​−−2001​=401​ V1​=55​401​−2001​ =2005​−2001​ V1​=2004​=501​ V=50 ∴d=50+4=54cm

Q. An astronomical telescope has objective and eyepiece of focal lengths $40 c m$ and $4 c m$ respectively. To view an object $200 c m$ away from the objective, at what distance the lenses must be separated (in $c m$ )?

$\frac{1}{V} - \frac{1}{- 200} = \frac{1}{40}$
$\frac{1}{V} = \frac{5}{5} \frac{1}{40} - \frac{1}{200}$
$= \frac{5}{200} - \frac{1}{200}$

$\frac{1}{V} = \frac{4}{200} = \frac{1}{50}$
$V = 50$
$∴ d = 50 + 4 = 54 c m$