An observer uses a refracting telescope in normal adjustment whose objective focal…
PHYSICS · Subjective · CBSE · Physics · Ray Optics and Optical Instruments · Ray Optics and Optical Instruments
Problem
An observer uses a refracting telescope in normal adjustment whose objective focal length is 90cm and eyepiece focal length is 6cm. She wants to increase the magnification to 25 by changing only the eyepiece while keeping the same objective.
(i) What focal length of eyepiece should she choose?
(ii) By how much will the length of the telescope tube change after the new eyepiece is fitted?