The distance between adjacent peaks of an electromagnetic wave is referred to as its

• A. Wavelength
• B. Frequency
• C. Amplitude
• D. Period

Answer: (A)

Wavelength is the spatial length of one full cycle of a wave, which is exactly the distance between neighboring peaks (or troughs) of an electromagnetic wave. This distinguishes it from frequency, which is how many cycles pass a point each second, from amplitude, which is the height of the wave, and from period, which is the time for one full cycle. In vacuum, wavelength and frequency are linked by λ = c / f, with c being the speed of light. So the distance between adjacent peaks—the spatial interval of one cycle—is the wavelength. For intuition, different colors of visible light have different wavelengths, from red around 700 nm to violet around 380 nm.