Question

Which of the following forms a virtual and erect image for all positions of the object?
A. Concave lens
B. Concave mirror
C. Convex mirror
D. Both (A) and (C)

Answer 1

The images formed would be clear if the nature of lens or mirror is known. Concave mirror and convex lens are diverging in nature, while convex mirror and concave lens are converging in nature. Convex lens is thicker towards the centre, while a concave lens is thinner towards its centre, hence they are diverging and converging respectively.

Complete answer:
A spherical mirror having curved reflecting surface on its inner side is known as concave mirror, while a spherical mirror having curved reflecting surface on its outer is known as convex mirror.
A concave lens is thinner towards its centre while it is thicker towards the edges. Convex lenses are thicker towards the centre while its edges are comparatively more straight and thin. Rays of light that pass through the lens are not brought closer together, that is; they diverge. Hence, a convex lens is a diverging lens. Convex lens is especially used in a camera.
In a concave mirror, the reflecting surface is on the outer side, so when the rays are incident on the surface, they are reflected back towards the focus on the same side of the incident rays, hence the rays converge on the same side. This is why the image that is formed is real and inverted.
In a convex mirror, the reflecting surface is on the inside, hence when the incident rays fall on the mirror, they are reflected. These reflected rays are diverging on the same side, hence when virtually taken on the other side and pointing towards the focus, we get a virtual and erect image.
Convex mirrors and concave lenses are diverging in nature. Thus, the reflected rays or even the refracted rays do not meet each other and they are produced to make them meet virtually. Therefore, the image that is formed is virtual and erect.

So, the correct answer is “Option D”.

Note:
Virtual and erect images are larger than the object and are also closer; hence convex mirrors are used in the side view mirrors of the cars they appear to be closer than they actually are. Concave mirror is used as a rear view mirror, because as they are diverging in nature, they give off a wider view as compared to convex mirrors.