What is a Spherical Mirror?
Spherical mirrors are the mirrors which have the shape of a piece cut out of a spherical surface. The surface may be either curved inwards or outwards. It can be defined as:
A spherical mirror is the mirror whose reflecting surface is part of a sphere.
Spherical mirrors can be of two types:
- Convex mirror
- Concave mirror
History of spherical mirrors in human civilization
- The first mirrors used by humans were most likely pools of water. The earliest known manufactured mirrors were polished stone pieces.
- Back in 500 AD, Chinese people began making mirrors with silver-mercury amalgams.
- Claudius Ptolemy conducted various experiments with curved polished iron mirrors.
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A spherical mirror whose reflecting surface faces towards the centre of the sphere i.e., curved inwards is known as a concave mirror.
Use of concave mirror:
- Satellite Dishes: One of the most important uses of a concave mirror is satellite dishes. These are used to receive the weaker signals sent from the communication satellites and then amplify it. These signals strike the concave mirror in parallel rays and get reflected back. These reflected rays are concentrated at the focus of the mirror. The main purpose of this mirror is to gather weaker signals coming from large areas and concentrate them at one point.
- Headlights in a car: A powerful source of light is kept at the focus point of the concave mirror in a smaller space at the back of the headlight. Any light striking the mirror from the focus will get reflected parallel to the axis of the concave mirror.
- Shaving mirror: Another use of concave mirror is a shaving mirror. The image formed after the reflections of the concave mirrors is helpful for people while shaving.
- Dentist’s mirror: The concave mirrors helps the dentist to focus light on the tooth to be examined.
A spherical mirror with a reflecting surface curved outwards is known as a convex mirror. It is a curved mirror where the reflective surface bulges out towards the light source
Uses of convex mirrors
- Rearview mirror: The side view mirror of the car forms a small and erect image with the help of convex mirrors which helps to see the way behind the car.
- Security mirrors in ATM: Security mirrors are kept near the ATM’s so that the bank customer can check that somebody is behind them or not.
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