Answer:
Frequency decreases
Wavelength increases
Explanation:
Frequency is how often a wave occurs. Wavelength is how long a wave is.
Waves that travel fast have a high frequency and short wavelength.
When they slow down, they have a lower frequency and longer wavelength.
Think about the electromagnetic spectrum: Gamma rays are fast, with high frequencies and short wavelengths (look bunched together). Radiowaves are slow, with low frequencies and long wavelengths (look stretched out).
