When two lenses are used in combination, the first one forms an image that then

Question

When two lenses are used in combination, the first one forms an image that then serves as the object for the second lens. The magnification of the combination is the ratio of the height of the final image to the height of the object. A 1.80cm -tall object is 53.0cm to the left of a converging lens of focal length 40.0cm . A second converging lens, this one having a focal length of 60.0cm , is located 300cm to the right of the first lens along the same optic axis.

Part A
Find the location and height of the image (call it I1) formed by the lens with a focal length of 40.0cm .

Part B

I1 is now the object for the second lens. Find the location and height of the image produced by the second lens. This is the final image produced by the combination of lenses.

Explanation / Answer

Part A) Use the lens equation

1/f = 1/p + 1/q

1/40 = 1/53 + 1/q

q = 163 cm [ image is 163 cm the the right of this lens]

The height is h'/h = -q/p

h'/1.80 = -163/53

h' = - 5.54 cm   ( -ve means inverted)

-------------------------------------------

Part B) Since the image for the first is 163 cm to the right of the lens, and the second lens is 300 cm to the right, that means that this image, which becomes the object for the second lens, is 137 cm to the left of that second lens

1/-60 = 1/137 + 1/q

q = -41.7 cm   (Image is 41.7 cm to the left of this second lens)

h'/h = -q/p

h'/-5.54 = -(-41.7)/(137)

h' = 1.69 cm   (It is upright)

Related Questions

Navigate

• Browse (All)
• Browse W
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.