Drawing Waves
Science: KS3, topic 3.3.29
Waves
Waves can be drawn, their properties depend on their waveform.
Drawing a wave
- Waves can have certain characteristics that can be drawn, usually waves are drawn as transverse waves.
- The crest or peak of a wave is the top of a wave.
- The trough is the bottom of a wave.
- Wavelength is the distance from one part of one wave to the same point on the next. IE peak to peak .
- The amplitude is the distance from its resting position (middle) to its peak or trough (The height of the wave).
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Longitudinal waves
- On longitudinal waves we can label:
- Compressions – when waves are close together.
- Rare-factions – when waves are further apart.
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Amplitude
- The amplitude is the distance from its resting position (middle) to its peak or trough (The height of the wave).
- If we increase the amplitude we will make it louder.
- So a small amplitude = small sound.
Loudness
- Loudness is measured in decibels.
- If sounds are too quiet we may not be able to hear them.
- If sounds are too loud they can damage our hearing.
- You can see amplitude on oscilloscope traces.
Pitch and frequency
- Pitch and frequency of sounds are related.
- Frequency is the number of waves that pass a point every second.
- Pitch is how low or high a sound is.
- A high pitch sound will have a high frequency, so will have more complete waves per second.
- The higher the frequency the closer together the waves will be.
- A low pitch sound will have a low frequency.
Hearing waves
- Humans can hear between the frequency of 20Hz to 20,000Hz.
- Below 20Hz is known as infrasound and it is the frequency elephants communicate in.
- Above 20000Hz is known as ultrasound and it is the frequency that bats and dolphins use for echolocation.
Test yourself on Drawing Waves
What are the correct relationships between loudness, amplitude, pitch, and frequency?
What is the unit for 'loudness'?
Two sound waves have the same amplitude. One sound is high pitched and the other is low pitched. What is different about these two waves when they are drawn?