Calculate the wave speed given a wavelength of 0.5 m and frequency of 20 Hz.

Calculate the wave speed given a wavelength of 0.5 m and frequency of 20 Hz.

• A. 10 m/s
• B. 5 m/s
• C. 100 m/s
• D. 1 m/s

Answer: (A)

The speed of a wave comes from multiplying its frequency by its wavelength: v = f × λ. Here the frequency is 20 Hz and the wavelength is 0.5 m, so v = 20 × 0.5 = 10 m/s. The units work out as meters per second because hertz means cycles per second. This is the speed you get with those two properties. If you changed either value, you’d get different speeds—for example, a wavelength of 0.25 m at the same frequency gives 5 m/s, a wavelength of 5 m gives 100 m/s, and a wavelength of 0.05 m gives 1 m/s.

The speed of a wave comes from multiplying its frequency by its wavelength: v = f × λ. Here the frequency is 20 Hz and the wavelength is 0.5 m, so v = 20 × 0.5 = 10 m/s. The units work out as meters per second because hertz means cycles per second. This is the speed you get with those two properties. If you changed either value, you’d get different speeds—for example, a wavelength of 0.25 m at the same frequency gives 5 m/s, a wavelength of 5 m gives 100 m/s, and a wavelength of 0.05 m gives 1 m/s.