Questions for the lens/mirror lab:
1. 1, You’ve no
doubt seen that the size of the image changes.
Comment on how/where it changes.
Knowing the theoretical focal length, can you determine a rule (or an
approximate rule) – something like, the image goes from smaller to larger when
do is equal to the focal length (or something like that). Be specific.
2. 2. How does the aperture affect the image? That is, if you were to block the top part of
the lens or mirror, how would the image change?
How about if you cover the bottom part?
3. 3. You should calculate theoretical focal lengths
for every point where you have data (do and di). How do these experimental focal lengths
compare to the theoretical focal length? Do a percent difference calculation for each.
4. 4, In general, have you found your results for
lenses and mirrors to be similar?
Discuss.
5. 5. In this lab, where did you see virtual
images? How did you know they were virtual?
6. 6. How could one determine (experimentally) the focal
length of a convex mirror or concave lens?
7. 7. Mathematically, there are worthwhile cases to
consider – key points – where do = f, do = 2f, do is much, much greater than f. What is going on mathematically with each of
these cases?
8. 8. Don’t forget to give errors and a general
conclusion. In your conclusion, discuss
the extent to which your initial suspicions (hypothesis) were correct or
incorrect.
Play around with this applet and note what
happens. This may make things easier to
visualize, even though only 2 or 3 rays are depicted as coming from the object.
There is a useful expression, the
magnification equation:
Magnification = -di/do
In this equation, a negative magnification
indicates an upside down image. If the
absolute value of the magnification is greater than 1, the image is
larger. You may want to calculate
magnifications to see how well they match with what you find to be in the lab
data.
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