Question

A distant object is viewed with a relaxed eye with the help of a small Galilean telescope having an objective of focal length $15$ cm and an eye piece of focal length $3$ cm.

• A. The distance between the objective and the eyepiece lens is $12$ cm
• B. The angular magnification of telescope is $5$
• C. Image of the object is erect
• D. The distance between objective and eye piece lens is $18$ cm

Answer 1

The correct option is A The distance between the objective and the eyepiece lens is $12$ cm

Given objective focal length $f_o$=15 cm and focal length of eyepiece$f_e$=3 cm

Now distance between eye piece and objective focal length$=15-3=12cm$

Also magnification$=\frac{f_0}{f_e}[1-\frac{f_e}{D}]=\frac{15}{3}[1-\frac{3}{12}]=\frac{15}{4}cm$