A driver sees a truck in the side mirror of a car.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A driver sees a truck in the side mirror of a car. The truck looks smaller than it is, and it seems farther away than it really is. Is the mirror plane, concave or convex? Why do car makers choose it, and what must the driver keep in mind?
Need a reminder? The key ideaShow
Concave mirror, object beyond : a smaller real inverted image between and . Object at : the same size, at . Object between and : a larger real image beyond . Object inside : a larger virtual upright image behind the mirror. A convex mirror always gives a smaller, virtual, upright image between and .
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. The size. A plane mirror keeps the size. A concave mirror can make things larger. Only a convex mirror always makes them smaller.
Step 2. Why choose it. A convex mirror shows a wide field of view: a large part of the road fits in a small mirror, and the image stays upright.
Step 3. The catch. Everything looks smaller, so it seems farther away. The driver must allow for this when judging a gap.
Answer: convex; it shows more of the road, but things are closer than they look.
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