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

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

  • 0
What are you looking for?