IP You have two lenses at your disposal, one with a focal length fi 37.5 cm, the

Question

IP You have two lenses at your disposal, one with a focal length fi 37.5 cm, the other with a focal length f2-37.5 cm Part A Which of these two lenses would you use to project an image of a lightbulb onto a wall that is far away? the lens with a focal length f? the lens with a focal length a Correct Part B If you want to produce an image of the bulb that is enlarged by a factor of 1.55, how far from the wall should the lens be placed? Submit Previous Answers Request Answer XIncorrect; Try Again; 2 attempts remaining

Explanation / Answer

You know that lens with focal length f1 should be used, So now using lens equation

1/f = 1/u + 1/v

f = focal length = 37.5 cm

Magnification is given by:

M = -v/u = -1.55

v = 1.55*u

Now

1/f = 1/u + 1/(1.55*u)

(1/u)*(1 + 1/1.55) = 1/37.5

u = 37.5*1.645

u = 61.69 cm

So

v = 1.55*61.69

v = 95.62 cm = 0.956 m

So object should be placed at 61.69 cm = 0.617 m

Please Upvote.

Please See that in language it wants the object distance which is 0.617 m, but in sign question wants image distance as 'di' which is 0.956 m. Please check both.

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