A concave mirror has a radius of curvature of 52 cm.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
- A concave mirror has a radius of curvature of . Find its focal length.
- A convex mirror has a focal length of . Find its radius of curvature, and say where its centre of curvature is.
Need a reminder? The key ideaShow
A concave mirror reflects from the inside of a sphere, and a convex mirror from the outside. The focus is half way between the pole and the centre of curvature : . A concave mirror has a real focus in front; a convex mirror has a virtual focus behind.
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) , in front of the mirror.
Step 2. (b) . A convex mirror is the outside of a sphere, so is behind the mirror.
Answer: (a) . (b) , behind the mirror.
Check. The focus is always half way between the pole and the centre of curvature.
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