Waves and Superposition

• The speed of sound is dependent on the medium it travels through.
• A difference between transverse and longitudinal waves is their direction of oscillation
• Transverse waves have perpendicular motion to the wave's direction
• Longitudinal waves have parallel motion with the wave's direction
• Light waves are electromagnetic waves that can be seen by our eyes
• Displacement (x) of a particle is its distance from its equilibrium position. The unit is the metre
• Wavelength (λ) is the distance between two consecutive points on a wave that are in phase. This means they vibrate together at any given time. The unit is the metre.
• Frequency (f) is the number of complete wavelengths passing a fixed point every second. The unit is hertz (Hz).
• Amplitude (y) is half the maximum displacement of a point on a wave from its equilibrium position. It is also known as the height or amplitude of the wave. The unit is the same as the displacement, which is metres.
• Period (T) is the time taken for one full oscillation, i.e., one cycle. The unit is seconds.
• Speed (v) is the rate of change of position with respect to time. In other words, it is the distance travelled divided by the time taken. The unit is m s⁻¹.
• The equation to calculate period is T = 1 / f
• The equation to calculate frequency is f = v / λ
• Phase difference is the fraction of a cycle between two oscillating particles, expressed in either degrees or radians
• Superposition states that when two or more waves meet at any point, they add together vectorially
• Constructive interference occurs when the peaks of two waves coincide, resulting in an increased amplitude
• If the phase difference between two waves is zero, then they will have constructive interference
• Destructive interference occurs when the troughs of two waves coincide, resulting in no net displacement
• If the phase difference between two waves is π (or -π), then they will have destructive interference
• When two waves are out of phase by half a wavelength, there will be complete destructive interference
• When two waves are out of phase by 90°, there is no resultant wave
• A standing wave is formed when two waves with equal amplitudes travel in opposite directions along a fixed string
• Intensity is the energy transmitted per unit time per unit area at right angles to the wave velocity
• The Doppler effect is the change in frequency of waves due to the relative motion of the wave source and the observer.
• Decreasing distance from the source increases the intensity of sound waves
• Reflection occurs when a wave bounces off an object without being absorbed
• The frequency increases when an moving sound source moves towards a stationary sound source.