Q:- How far should an object be placed from the pole of a converging mirror of focal length 20cm to form a real image of the size exactly 1/4 the size of the object?
 

Asked by Madhuchhanda Chakraborty | 24th Nov, 2014, 05:46: PM

Expert Answer:

begin mathsize 14px style Given : Focal space length comma space straight f equals minus 20 space cm space left parenthesis It space is space concave space mirror right parenthesis Object space distance equals straight u image space distance equals straight v Magnification comma space straight m equals fraction numerator minus straight v over denominator straight u end fraction equals fraction numerator minus 1 over denominator 4 end fraction space left parenthesis space Real space images space are space inverted space right parenthesis therefore comma space straight m equals plus straight v over straight u equals 1 fourth straight v equals straight u over 4 Mirror space formula comma space 1 over straight f equals 1 over straight u plus 1 over straight v fraction numerator 1 over denominator minus 20 end fraction equals 1 over straight u plus 4 over straight u equals 5 over straight u straight u equals minus 100 space cm The space object space should space be space placed space at space straight a space distance space 100 space cm space from space the space pole space of space concave space mirror. end style

Answered by Priyanka Kumbhar | 25th Nov, 2014, 09:32: AM

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