A student focuses a sharp image of the sun using a spherical mirror on a sheet of paper, which starts to burn after some time. Which of the following statement/statements about the mirror is/are correct?

(a)It is a concave spherical mirror

(b)It has a positive focal length

(c)It is a converging mirror ​​

Correct option is A

The correct answer is (a) Both (a) and (c)

Explanation:
• (a) It is a concave spherical mirror – Correct. A concave mirror is used to focus the parallel rays from the Sun to a single point (focus), generating heat that burns the paper.
• (c) It is a converging mirror – Correct. Concave mirrors are known as converging mirrors because they converge parallel rays to a focal point.
• (b) It has a positive focal length – Incorrect. As per the New Cartesian Sign Convention in optics, the focal length of a concave mirror is considered negative.

Information Booster:
• The ability of concave mirrors to focus light is used in devices like solar cookers, headlights, and shaving mirrors.
• The focal point of a concave mirror lies in front of the mirror, and all rays parallel to the principal axis converge at this point.

Additional Knowledge:

(b) It has a positive focal length (Option b)
• Focal length is positive for convex mirrors and negative for concave mirrors based on standard sign convention.
• Some sources may generalize or simplify sign usage, but the correct physics principle follows the Cartesian system.

(c) It is a converging mirror (Option c)
• Converges parallel rays to the focus.
• Commonly used in torches and solar devices.

(d) Both (b) and (c) (Option d)
• Incorrect as it wrongly assumes positive focal length for concave mirror.
• While (c) is true, (b) violates sign convention.