Solve question 10 Q10 A simple telescope consisting of an objective of focal length 60 cm and a - Physics - Ray Optics and Optical Instruments

Question

Solve question 10

Q10 A simple telescope consisting of an objective of focal length
60 cm and a single eye lens of focal length 5 cm is focussed on a
distant object in such a way that parallel rays emerge from eye
lens If the object subtends an angle of 20 at the objective, the
angular width of the image is

(A) 100 (B) 240 (C) 500 (D) (1/6)0

Sanat K Mukherjee · Accepted Answer

Dear Student,

Magnification of the telescope =Focal length of the objectiveFocal length of the eye lens = angular width of the imageangular width of the object60cm5cm=angular width of the image20angular width of the image = 12×20 = 240Ans (B)

From the option (4) it appears that the last zero of the angle is
not zero but the unit of angle i e , degrees
That is the angular width of the object is
2o and not 20 In that case, the angular width of the
image will be 24o
Regards,