Which formula correctly relates wave speed to frequency and wavelength?

Which formula correctly relates wave speed to frequency and wavelength?

• A. v = f / λ
• B. v = λ - f
• C. v = f λ
• D. v = f + λ

Answer: (C)

Think of wave speed as how far the wave travels in one second. The distance covered in one cycle is the wavelength, and the number of cycles per second is the frequency. Multiply these together: speed = frequency × wavelength. This gives the right units (1/s × m = m/s) and the right physical meaning: as either the wavelength or the frequency increases, the speed increases accordingly. For example, if the wavelength is 0.6 m and the frequency is 5 Hz, the speed is 0.6 × 5 = 3 m/s. Other forms would mix incompatible quantities or yield incorrect units (adding or subtracting wavelength and frequency, or dividing frequency by wavelength), so they don’t represent the actual relationship.

Think of wave speed as how far the wave travels in one second. The distance covered in one cycle is the wavelength, and the number of cycles per second is the frequency. Multiply these together: speed = frequency × wavelength. This gives the right units (1/s × m = m/s) and the right physical meaning: as either the wavelength or the frequency increases, the speed increases accordingly.

For example, if the wavelength is 0.6 m and the frequency is 5 Hz, the speed is 0.6 × 5 = 3 m/s.

Other forms would mix incompatible quantities or yield incorrect units (adding or subtracting wavelength and frequency, or dividing frequency by wavelength), so they don’t represent the actual relationship.