Question

Which of the following images can be obtained on screen?
A) Image formed by a plane mirror
B) Image formed by Concave mirror
C) Image formed by a convex mirror
D) None of the above

Answer 1

Hint: In optics, an image is defined as the meeting point of light rays coming from an object. A real image is the point of convergence made by converging rays, while a virtual image is the meeting point obtained by extensions of diverging rays. A real image is formed where rays converge, whereas a virtual image is formed where rays only appear to diverge from a point or converge to a point.

Complete step by step solution:
A real image is located in the plane of convergence of the light rays originating from a given object. A common example of a real image is the image on a cinema screen (the source being the projector and the screenplays as a diffusely reflecting surface), the image produced on a detector in the rear of a camera, and the image produced on the retina of an eye. In ray diagrams, real images are always represented by full, solid lines; extended rays of light, on the other hand, are represented by dashed lines.

Real images can be produced by a converging lens/mirror, that is, a convex lens or a concave mirror, only if the object is placed away from the focal point of the mirror/lens, and this real image is inverted. As the object approaches the principal focus, the image approaches infinity, and when the object passes the focal point the image becomes virtual and is not inverted (upright image).

From the above discussion, we can say that a real image is formed by a concave mirror and can be obtained on a screen.

Therefore, option (B) is the correct answer.

Note: A plane mirror always forms a virtual and erect image of an object, irrespective of the location of the object. Similar is the case with a convex mirror. In contrast to this, a convex lens forms real images but a concave lens mostly forms virtual images. Students are therefore advised not to confuse mirrors with lenses as images of almost opposite properties are formed by lenses and mirrors.