Light travels In a _________________ by virtue of _____________________.

• A. Wavelengths
• B. Frequency
• C. Amplitude
• D. Color

Answer: (A)

Light moves as waves, so it’s described by how far apart the wave crests are—the wavelength. The speed of a light wave in a medium equals its frequency times its wavelength. When light crosses into a different medium, its frequency stays the same, but the speed changes, so the wavelength must adjust accordingly. That link between propagation and wavelength is why talking about light traveling in wavelengths, governed by frequency, is the natural description. Amplitude relates to brightness, not how light travels; color is a perceptual effect tied to wavelength but doesn’t describe the mode of propagation.