Homework help or pointers anyone?

[peavey07]

homework help or pointers anyone?

A 1.29-cm-tall object is placed 31.1 cm to the left of a converging lens with a focal length f1 = 20.4 cm. A diverging lens, with a focal length f2 = -42.4 cm, is placed 31.1 cm to the right of the first lens. How tall is the final image of the object?


im not quite artistic enough to draw this picture for you sorry but any help or direction ect is appreciated

 

[peavey07]

got it

never mind! sorry i was stupid and missed a sign...had a positive in a number i should have had a negative

 

[mgb_phys]

Sign conventionas are always a problem in optics, it is useful to always draw a rough diagram and have a feel for where the image should be for an object in front and behind the focal poitn for a concave and convex lens.