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Convex Mirrors

For today's experiment we will be looking at a special kind of mirror.

All of you are pretty much familiar with the common plane mirror. It's flat and not very interesting. However, convex mirrors are quite different. Convex mirrors are a outward curving mirror. They bulge outwards to form a convex shape.

For this experiment you will need:-

- 1 convex mirror (Obviously..)

- 1 Laser pointer

- A piece of paper




Principle Axis (Denoted by letter "P") - The principal axis is an imaginary line which passes through the center of the mirror

Focus (Denoted by letter "F" - This is a point which lies on the principal axis, where the rays converge

In a convex mirror, the rays do not converge, they diverge.

The focus of a convex mirror is behind the mirror

Real VS Virtual image

This is a very important concept to remember in physics.

Whenever light rays converge to form an image, that image is called a real image.

Whenever light rays diverge to form an image, that image is called a virtual image.

Real images can be projected on a screen, while virtual images cannot be projected on a screen.

Since, light rays diverge to form a virtual image in convex lenses, the focus happens to be behind the mirror.


Ok so let's begin,

First take a piece of paper

And mark the focal length of the mirror (This will usually be mentioned on the packaging of the lens itself)

Once we do that, we will mount the mirror on a stand (The image shown in the picture is not the stand).

After mounting the mirror on the stand. Place an object to act as the screen for the reflection to be seen.

Here are three different ray angles for a convex mirror.

In this experiment i have taken a laser pointer and demonstrated a few of the many possible ray angles that can occur on a convex mirror.

Additionally you could also try moving the laser pointer up and down and observe what happens to the point then.

Let us now try to understand what exactly has happened here.

For this we are going to look at something called ray diagrams.

Ray diagrams are diagrams which map the reflection of light rays on a given mirror.

Let us look at a few examples.

(Courtesy - )

OKAY, Dont freak out. I know these look very ccomplicted but they all follow the same principle.

All light rays on a mirror follow a pretty basic law. It i known as the law of refelction

The law of reflection states that the angle which the incoming ray makes with the mirror is the same as the angle the outgoing ray makes.

In this case a ray coming into the mirror is governed by this law.

Another property of a conve mirror is that it is a "diverging lens".

Why is it diverging? you may ask me

Well if we look at the image we clearly see that the rays coming in are all going outwards, they are essentially diverging.

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