Answer:
their wavelength
Explanation:
A wave refers to disturbances or vibrations that travel from one medium or vacuum to another in an organized way, while wavelength refers to the distance between two consecutive peaks of waves.
For example, the wavelength of green light is 550nm (nanometre), while that of yellow light is 580nm (nanometre).
This difference in the color of the flashlights is visible to the human eyes because the human eye is believed to be able to detect any wavelengths of light from 700 nanometres to about 400 nm for violet light.
