(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A simple camera telephoto lens consists of two lenses. The objective lens has a focal length f1 = +36.0 cm. Precisely 33.0 cm behind this lens is a concave lens with a focal length f2 = -10.0 cm. The object to be photographed is 3.67 m in front of the objective lens.

(a) How far behind the concave lens should the film be placed?

(b) What is the lateral magnification (ratio of image height to object height) of this lens combination?

2. Relevant equations

1/f=1/d_{i}+ 1/d_{o}

M=-d_{i}/d_{o}

3. The attempt at a solution

My understanding is that the d_{i1}(the objective lens) is the d_{o2}(for the second/concave lens). Calculating d_{i1}gives me 0.399 m which is greater than the distance between the two lenses, so that would mean d_{o2}on the same side that the film would be on. I tried using 0.399m - 0.33 m = 0.069m = d_{o2}to calculate d_{i2}anyways, but that answer is wrong. I'm stuck as to what value to use for d_{o2}. As for part b) I know to find the magnification of each lens and then multiply the two magnification values to get the final magnification. I just need to figure out part a). Thanks so much for any help!

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Compound lenses final image

**Physics Forums | Science Articles, Homework Help, Discussion**