Find the power of (a) a convex lens of focal length 80 cm, and (b) a concave lens of focal length…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Find the power of (a) a convex lens of focal length , and (b) a concave lens of focal length .
Need a reminder? The key ideaShow
Power with in metres, in dioptres (D). Convex lenses have a positive power, concave lenses a negative power. For thin lenses in contact, the powers add: .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) , so .
Step 2. (b) , so .
Answer: (a) . (b) .
Common mistake. Do not put or into the formula: the focal length must be in metres.
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