CSEE (Form 4) Longitudinal Waves — practice questions

1. A longitudinal wave squeezes and stretches the medium along the direction it travels. 2. The squeezed region, where the particles are closest together, is a compression. 3. The stretched region, where the particles are furthest apart, is a rarefaction. _Source: Siyavula Physical Sciences Grade 10 (Everything Science, CC BY 4.0), Chapter 9: Longitudinal waves_

1. The frequency of a longitudinal wave is set by the vibrations of whatever created it. 2. Those vibrations are not altered by the wave entering a new medium. 3. The frequency is therefore always unchanged, irrespective of any changes in speed. 4. Because the period is the inverse of the frequency, the period stays the same as well. 5. Assuming a faster wave must have a higher frequency is the trap here. 6. It is the wavelength, not the frequency, that adjusts when the speed changes. _Source: Siyavula Physical Sciences Grade 10 (Everything Science, CC BY 4.0), Chapter 9: Longitudinal waves_

1. Speed, frequency and wavelength are tied together by the wave equation. 2. Speed equals frequency multiplied by wavelength. 3. The frequency is fixed by the source, so it cannot absorb the change. 4. For the product to grow while the frequency holds still, the wavelength must grow. 5. So the wavelength increases when the wave speeds up. 6. Choosing a smaller wavelength reverses the relationship and is the common error. 7. Zero wavelength would mean no wave at all, so that option cannot be right. _Source: Siyavula Physical Sciences Grade 10 (Everything Science, CC BY 4.0), Chapter 9: Longitudinal waves_