[Incompetent]

I can't seem to get graphs as I haven't really done many before. Must they start at 0 for both axes?

Also for 2007 concave mirror experiment can anyone tell me how I'm messing up? I took the data, got the inverse, and plotted it but it doesn't look much like the marking scheme one. I get an f value of ~13.9 (i've done it twice) which is a fair bit off the answer - 12.

This is my first attempt. I rounded numbers off quite early.

And my second attempt gave me a similar value but those two outliers weren't quite as serious.

[Neodymium]

Try converting u and v to metres, this gives you larger values for for their inverses which makes the graph a bit easier to plot. Also when you are drawing the line of best fit, make it so there are an equal number of dots at either side of the line. I got f=12.1cm when I did it.

As for starting with the origin that depends on the graph. For this graph it doesn't matter if you start from the origin. However when you are trying to prove two variables are directly proportional to each other (ie. a straight line going through the origin) then it is easier to start with the origin.

[IveSeenFire]

I think that eyelash at (0.054, 0.015) is the problem.