Theory:

Image formation in a plane mirror
The reflection of the object seen in the mirror is known as the image of the object.
A lighted candle is placed in front of a plane mirror. Here, the flame of the candle is seen in the mirror as if it is placed behind the mirror.
 
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The candle which is placed in front of the mirror is the object. The candle appearing at the backside of the mirror is the image of a candle.
 
Even when the candle is moved to different positions in front of the mirror, the image was upright in each position. The image of the candle flame appeared in a similar position as in the object. This type of image is called erect image.
Types of image
Image can be of two types. They are,
 
Virtual image
In the same candle activity, a vertical screen is placed at the back of the mirror to obtain the image of the candle. But, the image is not formed on the screen. Now, the screen is placed in front of the mirror to obtain the image of the candle, but still, the image is not obtained on the screen.
 
An image that cannot be obtained on a screen is known as a virtual image. The light rays from the object, which does not appear to meet at a point after the reflection from the mirror, forms a virtual image. The image formed on a plane mirror is always virtual.
 
A virtual image cannot be formed on a screen because it does not allow the light to pass through them.
 
Real image
An image that can be obtained on a screen is known as a real image. The light rays from the object, which meet after the reflection from the mirror, forms a real image.
 
Distance of image and object
This simple activity is to find the distance of the image of the object formed on the mirror. This requires a chessboard, a plane mirror, and a small object.
 
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  1. A chessboard is taken, and a plane mirror is vertically placed on the border.
  2. A small toy camera is placed on the boundary of the fifth square from the mirror.
  3. The position of the image formed on the mirror is noted.
  4. The object is again shifted to the boundary of the fourth square, and the position of the image is noted.
Inference
The image formed behind the mirror is at the same distance as the object in front of the mirror. This can be verified by placing the object anywhere on the board.