To remind you:
After you have done both the lens and mirror parts of the lab, start to look at your data for trends:
Is there a point where images go from bigger to smaller, real to virtual, etc.? Is this related to the approximate focal length (measured at the beginning of the trials? Start to think and write about this. Hint - there IS something to be seen, even if it's tough to tell from your data.
Check out this applet:
http://www.physics.metu.edu.tr/~bucurgat/ntnujava/Lens/lens_e.html
Move the object (arrow) and note what happens to the image. Think about this as it relates to your lab.
Now - calculate experimental focal lengths with your data (for convex lenses and concave mirrors), using the mirror/lens equation. Are these close to the approximate f (from outside)? Start thinking about sources of error.
Your lab will have the following:
- data
- discussion of trends seen
- calculation of f -- show a sample calculation (don't show ALL calculations, though all f's need to be calculated)
- sources of error
- general conclusion
Be sure to talk about how different your calculated f's are from the approximate f that you got from focusing on something outside.
A couple questions to answer:
1. How could one possibly determine the focal length of a convex mirror or concave lens? Is it possible to experimentally determine?
2. What should happen if you cover up part (or most) of the lens or mirror? Do you still get images? How are they affected?
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