I understand HOW to do the problem I just don\'t understand why you wouldn\'t us
ID: 2125671 • Letter: I
Question
I understand HOW to do the problem I just don't understand why you wouldn't use 31.0cm and Q1.
Also I don't generally understand how to determine if the image is real or virtual. I know that for upright or inverted is determined by neg of pos number for magnification. Just the real/ virtual I don't get.
Thanks in advance for the help!!!
Vanessa
Two converging lenses having focal lengths of 10.0 cm and 20.0 cm are placed 50.0 cm apart as shown in the figure below. The final image is to be located between the lenses at the position indicated, (a) How far to the left of the first lens should the object be positioned? (b) What is the overall magnification? (c) Is the final image upright or inverted?Explanation / Answer
You don't use the 31 because that is the distance measured from the first lens to the final image. The final image comes from the second lens. The initial image would come from the first lens.
Real images are determined by the sign of the image distance. If q is positive, the image is real. If q is negative, the image is virtual.
Hope this answers your question. If not, please ask for further assistance in the comments BEFORE you rate and I can help further. I used to teach this and can be of additional assistance if needed. Thanks!