Question

What kind of mirror is used as a search light reflector ?
(A) Concave mirror
(B) Convex mirror
(C) Plane mirror
(D) All the above

Answer 1

Hint: For search lights, we need an intense parallel beam of reflected light. After reflection a parallel beam of light gets produced which is used for searching objects.

Complete step by step answer:
Parabolic Concave mirrors with large apertures are used in search lights. In search light, we need an intense parallel beam of light for searching objects. When an object is placed at the focus of a concave mirror, the reflected rays are parallel to each other and also parallel to the principal axis. So, we place a source of light at the focus of the concave mirror.

So, the correct answer is “Option A”.

Additional Information:
Some other important uses of concave mirrors are :
1. A concave mirror is preferred to a plane mirror for shaving.
2. A concave mirror is used by dental surgeons as an inspection mirror to view the dental cavities.
3. A concave mirror is used in the ophthalmoscope.
4. The concave mirrors are used as reflectors in cinema projectors, magic lanterns, etc.

Note:
In search lights the concave mirror used should be of parabolic curvature. Spherical concave mirrors are not used in search lights. This is because in case of spherical concave mirrors, after reflection only the paraxial are reflected in a parallel beam. Marginal rays are not parallel after reflection. But in parabolic concave mirrors, all the rays (marginal and paraxial) become parallel to the principal axis after reflection. Thus the intensity of light in the reflected beam is increased which helps in searching objects.