# PHY 4

Waves and our Universe: Oscillations, Qunatum Physics and The universe

## Oscillations and waves: theory and definitions

Oscillation: A repeating movement of vibrations

Amplitude: Maximum Displacement from the equilibrium point

Period: Time taken for one oscillation

Frequency: No. of oscillations in one second

Wavelength: Length from one consecutive trough/ or peak to another

Periodic Motion: Movement that repeats itself in a regular manner.

Equilibrium Position: The position in which the resultant force on a body is zero, and in which the body would be at rest if not oscillating.

Uniform Circular Motion: A motion with a body travelling in a circular path with a constant speed.

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## Oscillations and waves: theory and definitions

Centripetal Force: Resultant force that has to act towards the centre of a circle, to make a body follow a circular path.

Centripetal Acceleration: Acceleration of a body following a circular path, and is directed towards the centre of the circle.

S.H.M: oscilatory motion, where the acceleration/Force is directly proportional to the displacement, in the OPPOSITE direction.

Harmonic Oscillations: A set of many oscillations, whose displacements as a function of time very accordingly to, sine or cosine functions.

Phase Difference: A measure of how much waves are in step or out of step

Path Difference: Difference in distance travelled by each wave.

Anti-Phase: Out of step(xactly)

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## Oscillations and waves: theory and definitions

Natural Frequency: The frequency at which a free-standing system oscillates Resonance: The large amplitude oscillations that arise when an oscillatory system is driven at a frequency equal to its' natural frequency. Travelling wave: A wave that TRANSFERS energy. Transverse wave: a wave where the displacements/vibrations are perpendicular to the direction of propagation. Longitudinal wave: a wave where the displacements/vibrations are parallel to the direction of propagation. Plane Polarised: Vibrations are confined to a single plane, perpendicular to the direction of energy propagation. Unpolarised wave: Vibrations occur in a large No. of planes, perpendicular to the direction of energy propagation. Diffraction: The spreading out of a wave as it passes through an aperature. Refraction: The change in direction of a wave as it passes from one medium into another, in which it has a different speed.

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