Which of the following is used in the rear-view mirrors of vehicles?
A. Plane mirror
B. Convex mirror
C. Concave lens
D. Any of these

Hint: We will discuss the mirrors available and the properties of which will be best suited for use as the rear-view mirror in the vehicle. Then we will discuss the precautions to be taken when using a rear-view mirror based on the properties of the image formed.

Complete answer:
If we use a plane mirror, we will see the area behind us, but due to the limitations of its shape and size, the area visible will be very small and limited view will be offered. Next when we use a concave mirror, a real image will be formed at the focus as the light rays coming from the vehicles in the rear can be considered almost parallel and will converge at the focus. We will also need a screen to obtain the image, this is definitely not possible inside a car and thus, it won’t be used. Now for a convex mirror as the light rays will come almost parallel to the mirror, they will all make a virtual image at the focus and it will be easy to view them and they will also cover a very large area behind the vehicle. So, as we can see that a convex mirror is best suited to be used as a rear-view mirror of a vehicle. Hence, the correct option is B, i.e. Convex mirror.

So, the correct answer is “Option B”.

Note:
Take care that the images formed in the rear-view mirror will be closer to you than they appear. This is due to our brains being so used to seeing plane mirrors that we assume it to be a plane mirror and interpret the image accordingly.