Question

We wish to obtain an erect image of an object, using a concave mirror of focal length $15cm$. What should be the range of distance of the object from the mirror? What is the nature of the image? Is the image larger or smaller than the object? Draw a ray diagram to show the image formation in this case.

Answer 1

Step 1: Concept used

Concave mirrors are the outer surface of a hollow sphere that is cut and painted from the outside. The inner surface of this cut part act as the reflecting surface.

Characteristics of concave mirrors:

• Light converges at a point when it strikes and reflects back from the reflecting surface of the concave mirror.
• It also acts as a converging mirror.
• When the concave mirror is placed very close to the object, a magnified and virtual image is obtained.
• The image formed by the concave mirror can be small or large or can be real or virtual.

Step 2: Range of distance of the object from the mirror

1. The distance of an object in the concave mirror should be less than the focal length for the formation of an erect image.
2. Hence, the range of distance between the object from the mirror will be $0\mathrm{cm}$ to $15\mathrm{cm}$ in the front of the mirror from the pole. The nature of the image will be virtual and erect.
3. The image is formed by a concave mirror, the size of the image will be larger than the object.

Step 3: Ray diagram to show the image formation