Question

For a concave mirror, whenever the distance of the object is less than the focal length, the image is virtual. That is called virtual image, because:
A. the image is formed behind the mirror
B. the image is not inverted
C. the image cannot be obtained on screen
D. the image can be located by virtue of parallax

Answer 1

Hint: When the object is placed between the focal point and pole of a concave mirror then the image is formed behind the concave mirror. Now, when the image is formed behind the mirror, the image is said to be a virtual image.

Complete step by step solution:

Let as consider an image AB is placed between the pole (P) and focal point (F) in the point of a concave mirror. Now for making an image with the help of ray diagram into the mirror minimum two rays are required. Now let one ray be taken from the (A) of the object it strikes into the surface of the concave mirror and after reflection, say it possesses through the centre of concave (C) of the mirror. Again now the second ray is taken from the (B), it strikes into the surface of the concave mirror at the pole (P) and it reflects back at the same angle of reflection (R) as angle of incidence (i).
Now the reflected rays seems to coming from a point ${A^l}$ of the image, and a point ${B^l}$ from principal axis joining the point ${B^l}$ to ${A^l}$ image is farmed. This image is behind the mirror so it should be a virtual image.

Hence, option (A) is correct.

Additional Information: If the image is formed behind then it is said to be a virtual image.

Note: If the ray is coming or seems to be coming from the centre of curvature of the mirror, then after reflection it will always pass through the centre of curvature.