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A concave mirror and convex mirror are cut from same spherical glass ball but the aperture of concave mirror is more than the aperture of convex mirror. What can be said about their focal lengths?

A concave mirror and convex mirror are cut from same spherical glass ball but the aperture of concave mirror is more than the aperture of convex mirror. What can be said about their focal lengths? Correct Answer Both have same focal length

 Concept:

Spherical mirror:

  • A spherical mirror is a mirror whose reflecting surface is part of a hollow sphere of glass.
  • It is also called a curved mirror.
  • It can converge and diverge the parallel rays of light that fall on them
  • A spherical mirror is a part of a hollow sphere in which one plane is raised and the other plane is suppressed.
  • There are two types
    • Concave mirror 
    • convex mirror

Concave Mirror 

  • A concave mirror is called a mirror in which the central part of the reflecting surface is inwards.
  • It is also called a converging mirror.
  • Rays of light coming parallel to the principal axis of a concave mirror, after reflection meets at a common point on the principal axis. This point is called Focus.
  • The focus of the concave mirror is real.

Convex Mirror

  • A convex mirror is called that in which the central part of the reflecting surface is outwards.
  • It is also called a diverging mirror.
  • Rays of light come parallel to the principal axis of a convex mirror, after, diverging. The divergent rays being produced backward meet at a common point on the principal axis.
  • The focus of the convex mirror is imaginary.

Explanation:

  • Focal Length is the distance between the pole and the principal focus.
  • So, the focal length of a spherical mirror that is the convex and concave mirror is equal to half of the radius of curvature of the spherical mirror. Thus, the focal length of both the mirror remains the same.

Therefore, from the above explanation; we can say that the correct answer is both have the same focal length.

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