physics notes

1. Reflection of waves occur when a wave strike an obstacle. The wave undergoes a change in the direction of propagation when it is reflected.
2. The incident wave is the wave before it strikes the obstacles, whereas the reflected wave is the wave which has undergone a change in direction of propagation after reflection.


3. The Phenomenon of reflection of waves obeys the Laws of Reflection where:
i) The angle of incidence, i is equal to the angle of reflection, r.
ii) The incident wave, the reflected wave and the normal lie in the same plane which is perpendicular to the reflecting surface at the point of incidence.

Applications of reflection of Waves in Daily Life

Safety

i) The rear view mirror and side mirror in a car are used to view cars behind and at the side while overtaking another car, making a left or right turn and parking the car. The mirrors reflect light waves from other cars and objects into the driver's eyes.

ii) The lamps of a car emit light waves with minimum dispersion. The light bulb is placed at the focal point of the parabolic reflector of the car lamp so that the reflected light waves are parallel to the principal axis of the reflector. Parallel light waves have a frther coverage.

Defence


i)A periscope is an optical instrument. It can be constructed using two plane mirrors for viewing objects beyond obstacles. The light waves from an object which is incident on a plane mirrorin the periscope are reflected twice before entering the eyes of the observer.

Telecommunications

i) Infrared waves from the remote control of an electrical equipment (television or radio) are reflected by objects in the surroundings and received by the television set or radio.