Converging Mirror or Concave Mirror

Converging Mirror or Concave Mirror

Concave Mirror can be considered as a part of a sphere. Consider a hollow glass sphere and cut a piece of the sphere as shown in the figure. The cut off piece has two surfaces, one which is bulging out or convex surface and other is a hollow surface that is on the same side as the centre of the original sphere is called as concave surface.

If we polish the bulging surface or convex surface with silver and look at it from the hollow side or concave surface, we have a concave mirror. These mirrors, which are referred to as convergent mirrors, concentrate the light rays, coming parallel to the principal axis causing them to converge on to a point known as the focal point. Concave mirrors form real images that can be projected on to a screen if the object is farther away than the focal point. The image obtained is large if formed near the focal point or small if formed far away from the focal point. In both cases, the image is reversed. If we place the object closer than the focal point, the image is formed upright and large but virtual (i.e., it cannot be projected).

Reflection Through Concave Mirror :

When a narrow beam of light traveling parallel to the principal axis is incident on the reflecting surface of a concave mirror,as shown in the figure, each ray is reflected according to the laws of reflection and converge to a point F on the principal axis known as the focus. As the rays are converging after reflection the concave mirror is also called converging mirror.

USES OF CONCAVE MIRRORS:

Concave mirrors are commonly used in torches, search-lights and vehicles headlights to get powerful parallel beams of light.

Concave mirrors are used as shaving mirrors to see larger image of the face.

Dentists use concave mirrors to see large images of the teeth.

Large concave mirrors are used to concentrate sunlight to produce heat in solar furnaces.

Sample Questions

(More Questions for each concept available in Login)

Question : 1

A ray of light passing through the focus of a concave mirror will be _________________
A. Absorbed by the mirror		B. Absorbed through the focus again
C. Reflected through the centre of curvature of the mirror		D. Reflected parallel to the principal axis of the mirror.
Right Option : D
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Question : 2

Large _________________ are used to concentrate sunlight to produce heat in solar furnaces.
A. Concave mirrors	B. Convex mirrors	C. Concave lens	D. Convex lens
Right Option : A
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Question : 3

Which of the following is known as converging mirror ?
A. Convex mirror	B. Concave mirror	C. Both (a) and (b) are correct.	D. None of these
Right Option : B
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