# 1/f=1/u+1/v what is f,u and v?

1. Apr 30, 2015

### gracy

Have I labeled correctly?

2. Apr 30, 2015

### Staff: Mentor

This looks like it should be posted in the schoolwork forums, gracy. And are you familiar with the thin lens formula? That is basically what you are asking about. Check it out on wikipedia for more info.

3. Apr 30, 2015

### Staff: Mentor

Almost. u and v are correct, but not f. f is the focal length of the lens, not the distance from lens to image. (That's what v is.) Look it up!

4. May 1, 2015

### gracy

I got you point.I think the image below greatly explains all the three f,v,u.

I was doing following mistakes.
1-I was not considering focal point . If the light rays converge (as in a converging lens), then they will converge to a point. This point is known as the focal point of the converging lens. If the light rays diverge (as in a diverging lens), then the diverging rays can be traced backwards until they intersect at a point. This intersection point is known as the focal point of a diverging lens.
2-I was confused about focal length.Focal length is distance between optical center and focal point.
3-All the distance should be measured from optical center.So ,in the previously attached image i.e

u and v was not correct in the sense that the distance was not measured from optical center.I think that's what you meant by

Last edited: May 1, 2015
5. May 1, 2015

### sophiecentaur

@gracy
Do you have a good old fashioned School Physics Text Book? Many of the questions you have been asking (on this and other topics) are dealt with in books and you can usually rely on them to get things right.
It may depend upon which part of the world you are getting your Science education and I know there are some ridiculously elementary Science courses in some places. If your course is badly lacking, then you really should invest in a decent book. These days, the Internet can get any book to anybody, anywhere. It may be your best way forward.