Starter quiz
- Waves on a string are ______ waves.
- transverse ✓
- longitudinal
- electromagnetic
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- What is 12 cm in metres?
- 0.012 m
- 0.12 m ✓
- 1.20 m
- 12 m
- 12 000 m
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- Some waves on a string have a frequency of 3 Hz and a wavelength of 12 cm. How would you calculate the wave speed in m/s?
- 3 x 12
- 3 x 0.12 ✓
- 3 ÷ 12
- 3 ÷ 0.12
- 0.12 ÷ 3
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- In experiments, what are the different types of variables?
- independent variable⇔what you change in each test to see what effect it has ✓
- dependent variable⇔what you monitor to see if it changes in response ✓
- control variables⇔what you keep the same so they don't affect the results ✓
- When a wave travels along a string, what is the wave medium?
- the middle point of a wave, halfway along a wavelength
- the frequency of the wave
- the string ✓
- the equilibrium position
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- If waves of different frequencies and wavelengths all have the same speed, what happens if you increase the frequency of waves?
- increasing the frequency also increases the wavelength
- increasing the frequency decreases the wavelength ✓
- increasing the frequency does not affect the wavelength
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Exit quiz
- In an experiment, a variable that must be kept the same so it does not affect the results, is called a ______ variable.
- 'control' ✓
- Which images show a standing wave on a string?
The length of string oscillating in this image is 90 cm. What is the wavelength of the waves?- 30 cm
- 60 cm ✓
- 90 cm
- 180 cm
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- Starting with the measurement of the string length, put the steps in order to find the speed of waves on a string from a standing wave pattern.
- 1⇔Measure the length of the string using a metre rule.
- 2⇔Slowly increase the frequency of the oscillator until a standing wave is seen.
- 3⇔Record the frequency from the signal generator and work out the wavelength.
- 4⇔Calculate the wave speed using speed = frequency x wavelength.
- Suggest which of the following could affect the speed of waves on a string?
- The frequency of the waves
- The wavelength of the waves
- The amplitude of the waves
- The tension of the string ✓
- The density of the string ✓
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- Waves on a string have a frequency of 10 Hz and a wavelength of 20 cm. The frequency is increased from 10 Hz to 40 Hz. Nothing else changed. How would the wavelength be affected?
- The wavelength would reduce from 20 cm to 5 cm ✓
- The wavelength would reduce from 20 cm to 10 cm
- The wavelength would stay the same
- The wavelength would increase from 20cm to 40 cm
- The wavelength would increase from 20 cm to 80 cm
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Worksheet
Presentation
Video
Lesson Details
Key learning points
- To find standing wave frequencies, increase the frequency of the oscillator until a standing wave pattern is seen.
- The wavelength of the waves can be found from the length of the oscillating string and the standing wave pattern
- The speed of waves on a string only depends on the properties of the wave medium (the string).
- For waves on a string, frequency and wavelength are inversely proportional
- Control variables are the quantities that must be kept the same during experiments so they don’t affect results.
Common misconception
Frequency or wavelength of waves on a string will affect the wave speed.
The speed of waves on a string only depends on the properties of the wave medium (the string) e.g. tension, density
Keywords
Standing wave - A standing wave is a stable pattern of oscillation that does not appear to travel across a wave medium.
Tension - Tension is the name for the force applied to a stretched string or rope. Without any tension a string or rope would be slack.
Inverse - Division is the mathematical inverse (opposite) of multiplication, so the inverse of ×2 is ÷2 (which can also be written as ×½).
Proportion - A proportion is an exact mathematical comparison, such as double, half (50%), triple, a third, quadruple, a quarter etc.
Control variable - Control variables are the quantities that must be kept the same during experiments so they don’t affect results.