Question

30. A convex lens forms a real an inverted image of an object at a distance of 40
centimeters from it. what will be the distance of an object if size of an image is same as
the object? Determine the power of lens.​

Answer 1

Answer:

For the image to be of same size i.e magnification =1

distance of object = distance of image

i.e u=v=40

so u=-40

v=40

adjusting the signs.

1/f=1/v+1/u=1/40+1/40=2/40=1/20

f=20

Power = 100/f=100/20= + 5 D