Which color has the longest wavelength?

• A. Red
• B. Blue
• C. Green
• D. Violet

Answer: (A)

Visible light comes in a range of wavelengths, and the color you see depends on where the light lies in that range. In the visible spectrum, longer wavelengths appear toward the red end and shorter wavelengths toward the violet end. Among the colors shown, red has the longest wavelength—about 620 to 750 nanometers—while blue, green, and violet have shorter wavelengths. So red is the color with the longest wavelength in this set.