Spherical Mirrors: Terms MCQs Quiz | Class 10

This quiz is designed for Class X students, covering Science (Code 086) from Unit III: Natural Phenomena. Test your knowledge on Spherical Mirrors and their fundamental terms including Centre of curvature, principal axis, principal focus, and focal length. Submit your answers and download a detailed PDF of your results with correct answers.

Understanding Spherical Mirrors: Key Terms

Spherical mirrors are highly polished reflecting surfaces that are part of a hollow sphere. They are broadly classified into two types: concave mirrors and convex mirrors. To understand how these mirrors form images, it’s crucial to grasp the fundamental terms associated with them.

1. Centre of Curvature (C)

The Centre of Curvature is the center of the hollow sphere of which the spherical mirror is a part. It is denoted by the letter ‘C’. For a concave mirror, the centre of curvature lies in front of the reflecting surface, while for a convex mirror, it lies behind the reflecting surface.

2. Principal Axis

The Principal Axis is an imaginary straight line passing through the pole (P) and the centre of curvature (C) of the spherical mirror. It is the main reference line for all measurements and ray diagrams related to the mirror.

3. Principal Focus (F)

The Principal Focus is a specific point on the principal axis of a spherical mirror where rays of light parallel to the principal axis converge (in the case of a concave mirror) or appear to diverge from (in the case of a convex mirror) after reflection.

  • Concave Mirror: Parallel rays of light, after reflection from a concave mirror, actually meet at a point on the principal axis. This point is the real principal focus (F).
  • Convex Mirror: Parallel rays of light, after reflection from a convex mirror, appear to diverge from a point behind the mirror on the principal axis. This point is the virtual principal focus (F).

4. Focal Length (f)

The Focal Length is the distance between the pole (P) of the spherical mirror and its principal focus (F). It is denoted by ‘f’. The focal length is a crucial property of a spherical mirror as it determines its image-forming capabilities.

Relationship between Focal Length (f) and Radius of Curvature (R):

For spherical mirrors with small apertures, the focal length is approximately half of the radius of curvature. This relationship is given by the formula: f = R/2.

This means that the principal focus (F) lies exactly midway between the pole (P) and the centre of curvature (C).

Quick Revision Summary

  • Centre of Curvature (C): Center of the sphere the mirror is part of.
  • Principal Axis: Line passing through P and C.
  • Principal Focus (F): Point where parallel rays converge (concave) or appear to diverge (convex) after reflection.
  • Focal Length (f): Distance from P to F.
  • Relationship: f = R/2.

Practice Questions

  1. The imaginary line passing through the pole and the centre of curvature of a spherical mirror is called the:
    1. Aperture
    2. Focal plane
    3. Principal axis
    4. Reflecting surface

    Correct Answer: c) Principal axis

  2. For a concave mirror, where do parallel rays of light converge after reflection?
    1. At the centre of curvature
    2. At the pole
    3. At the principal focus
    4. Between pole and focus

    Correct Answer: c) At the principal focus

  3. What is the relationship between the radius of curvature (R) and the focal length (f) of a spherical mirror?
    1. R = f
    2. R = 2f
    3. f = 2R
    4. f = R/4

    Correct Answer: b) R = 2f

  4. The principal focus of a convex mirror is:
    1. Real and in front of the mirror
    2. Virtual and in front of the mirror
    3. Real and behind the mirror
    4. Virtual and behind the mirror

    Correct Answer: d) Virtual and behind the mirror

  5. The distance between the pole and the principal focus of a spherical mirror is known as the:
    1. Radius of curvature
    2. Focal length
    3. Aperture
    4. Principal axis

    Correct Answer: b) Focal length