# real image formation by plane mirror

In this diagram:

Why are reflected rays extended with some angle with the mirror so as to form the real source? I tried to extend them without deviations but the rays wouldn't meet. Is the diagram wrong or is there a reason behind it?

That image is a completely wrong one.

Image can be formed by producing the light rays backwards. Such an image is called a virtual image, as the light rays do not actually intersect, but only do so when produced backwards. For this:

1. One should draw a light ray from the point (whose image has to be formed) to the mirror.

2. A normal or perpendicular has to be drawn at the point of contact of the light ray with the mirror.

3. The angle of the ray from the normal has to be calculated.

4. Another ray from the point of incidence, at that angle to the normal, is drawn, which may be produced backwards.

Also, one may, after drawing the first ray of light,

1. First plot the top and bottom points of the object on the other side of the mirror, keeping in mind that image distance = object distance.

2. From this point, the second ray of light may be directly drawn to the point of incidence of the previously drawn ray of light, on the mirror. In this case, the angle is not required.

But, the necessary condition for formation of virtual image is that, there has to be at least two light rays from each point. Two light rays at least are needed from each of the top and bottom of the candle to form an image, otherwise the intersection of rays cannot be shown.

Hence the diagram is wrong.

This is a better correct similar diagram:

• actually i was asking for the diagram below it....can u comment on that also. Commented Oct 9, 2017 at 17:07
• the site is -quora.com/… Commented Oct 9, 2017 at 17:08
• If you're speaking about the next one that is hand drawn (is it?), then that is also wrong. See, two light rays start from the top and bottom, but on the other side of the mirror, they intersect at the image of the top of the source. So, the image is incorrect. Two light rays should start from each of the top and bottom, and then intersect to form the image if the upper part, and that of the lower one. Commented Oct 9, 2017 at 17:12
• See the image I've just added. It should be like that. @user42172 Commented Oct 9, 2017 at 17:15