-->

Wave Optics

Question
CBSEENPH12039953

In an astronomical telescope in normal adjustment, a straight black line of length L is drawn on inside part of the objecitive lens. The eye - piece forms a real image of this line. The length of this image is I. The magnification of the telescope is 

  • straight L over straight I space plus space 1
  • straight L over straight I space minus space 1
  • fraction numerator straight L plus 1 over denominator straight L minus 1 end fraction
  • straight L over straight I

Solution

A.

straight L over straight I space plus space 1
We know, magnification of telescope, we have
straight M space equals space straight f subscript straight o over straight f subscript straight e
Here space
fraction numerator straight f subscript straight e over denominator straight f subscript straight e plus straight u end fraction space equals space fraction numerator negative straight I over denominator straight L end fraction

rightwards double arrow fraction numerator straight f subscript straight e over denominator straight f subscript straight e minus left parenthesis straight f subscript straight o plus straight f subscript straight e right parenthesis end fraction space equals space fraction numerator negative straight I over denominator straight L end fraction

rightwards double arrow space straight f subscript straight e over straight f subscript straight o space equals space straight I over straight L space straight i. straight e space
straight M space equals space straight L over straight I

Some More Questions From Wave Optics Chapter