Question

Three thin lenses, each with a focal length of 40.0 cm, are aligned on a common axis; adjacent lenses are separated by 52.0 cm.

A)Find the position of the image of a small object on the axis, 80.0 cm to the left of the first lens.

Answer 1

the first lens

Apply 1/f = 1/p + 1/q

Put values..

1/40 = 1/80 + 1/q

q = 80 cm

That means the image is 80 - 52 = 28 cm behind the second lens...

1/40 = 1/-28 + 1/q

q = 16.48 cm behind the second lens.

That means the second image is 52 - 16.48 = 35.52 cm in front of the third lens

1/40 = 1/35.5 + 1/q

q = -315.6 cm

Thus the final image is 315.6 cm to the left of the third lens which is 211.6 cm to the left of the first lens which is 131.6 cm to the left of the original object.

I hope help you.....