my physics homework. again. please help? yeah I know I shouldn\'t be asking peop

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my physics homework. again. please help?
yeah I know I shouldn't be asking people on the net to do myhomework for me, but there are just some things you won't be ableto understand by reading just a book or two.. it's due soon and Idon't think I'll be able to comprehend and answer this in so littletime. . So if anyone will help, I would very much appreciateit.

Thank you very much!

Please no spams. I really need REAL answers to my questions.

It would be great if you just give me clues on how to answer them,because I really have no idea how, to be honest. And I've read therules about posting questions. I hope it's okay that I includedanother question cause I just typed everything my textbook wants meto answer.

A converging lens with a focal length of 90.0 cm forms an image ofa 3.20-cm-tall real object that is to the left of the lens. Theimage is 4.50 cm tall and inverted. Where are the object and imagelocated in
relation to the lens? Is the image real or virtual?

Explanation / Answer

If the distances from the object to the lens and from the lensto the image are S1 and S2respectively, for a lens of negligible thickness, in air, thedistances are related by the thin lens formula: (1/S1) + (1/S2) = (1/f)----------(1) the magnification of the lens is given by m = (I/O) or (S2/S1) = (I/O) f = 90.0 cm,I = 3.20 cm and O = 4.50 cm or (S2/S1) = (3.20/4.50) = (32/45) or S2 = (32/45) * S1------------(2) from (1) and (2) we get (1/S1) + (1/(32/45) * S1) = (1/f) or (1/S1) + (32/45 * S1) =(1/90.0) solving the above equation for S1 we get S1 = 154 cm from (2) we get S2 = (32/45) * 154 = 216.5 cm If an object is placed at a distanceS1 along the axis in front of a positive lensof focal length f, a screen placed at a distanceS2 behind the lens will have a sharp image ofthe object projected onto it, as long as S1> f (if the lens-to-screen distanceS2 is varied slightly, the image will becomeless sharp). This is the principle behind photography and the humaneye. The image in this case is known as a real image.

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