Waves and Related Concepts (Video Notes)

Progressive wave

A wave where the disturbance travels through space, transferring energy from one location to another.

Displacement

The distance of a point on a wave from its undisturbed (equilibrium) position.

Amplitude

The maximum displacement of a particle from its undisturbed position.

Period

The time taken for one complete oscillation.

Frequency

The number of oscillations per unit time.

Wavelength

The distance between successive points in phase, e.g., crest to crest.

Wave speed

The speed at which the waveform travels in the direction of propagation (v).

Phase difference

The difference in phase between two points or waves, measured in radians or degrees.

In phase

Phase difference equal to 0 (or multiples of 2π); the waves are in step.

Antiphase

Phase difference of π (180°); waves are exactly out of step.

Cathode-Ray Oscilloscope (CRO)

An instrument used to display waveforms and measure frequency and amplitude.

Y-gain

Vertical gain control on a CRO that sets the amplitude scale (voltage per division).

Time-base

Horizontal sweep control on a CRO that sets the time per division, used to determine period and frequency.

Intensity

Rate of energy transmitted per unit area perpendicular to the direction of wave propagation; units W m⁻².

Point-source intensity formula

I = P / (4π r²), where P is the radiated power and r is the distance from the source.

Doppler effect

Change in observed frequency due to relative motion between the source and the observer.

Observed frequency (blue/red shift)

Frequency perceived by an observer; increases (blue shift) as the source approaches, decreases (red shift) as it recedes.

Transverse wave

A wave in which oscillations are perpendicular to the direction of propagation (polarization can