If the frequency remains constant, the wavelength increases. The wavelength decreases as the frequency decreases. The frequency increases as the wavelength decreases. If the wavelength remains constant, the frequency increases.
I gave my students this multiple choice question: Which of the following best describes the relationship between frequency and wavelength of electromagnetic waves?

Only one answer is correct among these 4 choices:
- If the frequency remains constant, the wavelength increases.
- The wavelength decreases as the frequency decreases.
- The frequency increases as the wavelength decreases.
- If the wavelength remains constant, the frequency increases.

Could you tell me which one is correct?

The frequency increases as the wavelength decreases.