A longitudinal wave enters a medium where its speed increases while its frequency stays the same. What happens to the wavelength?

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_