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# Wave properties for Edexcel A-level Physics

1. Wave amplitude
2. Wavelength
3. Wave frequency
4. Wave period
5. Wave speed
6. Phase and phase difference

A waveโs amplitude is a measure of its maximum height from its rest position.

The wavelength (ฮป) of a wave can be shown in a diagram or it can be calculated using the formula: Wavelength = wave speed รท frequency.

The frequency of a wave is the number of waves that pass a certain point per second. It can be calculated using the waves time period, or speed and wavelength.

The time period of a wave is the time it takes a full wave cycle to pass a certain point. It is often calculated using the equation: Time Period = 1 รท frequency.

Wave speed is the distance travelled by a wave divided by the time it takes. The wave equation can be used to work out the speed of a wave.

When talking about phase difference (ฯ) we can be referring to two separate waves, or two particles in the same wave, and it tells us how far or behind one wave/ particle is from another. Phase difference is measured in radians or degrees and values can range from 0 to 2ฯ or 0 to 360ยฐ with the value of ฯ being half a wavelength. In the diagram particles 1 and 3 are in phase, but 1 and 2 are ฯ radian out of phase with each other.

# 1

Using the diagram, calculate the speed of the wave shown if it has a wavelength of 25 m.

Speed = Wavelength รท Time Period. V = ฮป รท T, V = 25 รท 10 = 2.5 m/s.

# 2

The vertical displacement of a point on a wave doubles when the amount of energy in the wave doubles. What is the effect on the amplitude of the wave?

It doubles.

# 3

State the value of 2 ยฝ ฮป in terms of radians and degrees.

2 ยฝ ฮป = 2 full wavelengths + ยฝ a wavelength = 5ฯ rad but this can be simplified to remove complete wavelengths = ยฝ ฮป = ฯ rad or 180ยฐ.

# 4

What is the definition of wavelength?

The wavelength is the distance covered by a full cycle of a wave, this is usually measured as the distance between two peaks or two troughs.

# 5

If two particles are half a wavelength apart, what is their phase difference in terms of radians?

1 ฮป = 2 ฯ, ยฝ ฮป = ฯ rad.

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