What is the wavelength of red light?

Red light is part of the visible light spectrum, which ranges approximately from 380 nm to 750 nm. The wavelength of red light specifically falls towards the longer end of this spectrum. The options given indicate various wavelengths in nanometers (nm), with red light typically having wavelengths that start from about 620 nm and can extend up to about 750 nm.

The choice of 700 nm is consistent with the understanding that it represents a wavelength within the red portion of the visible spectrum. It is important to recognize that while other options provided are associated with different colors of light—390 nm corresponds to violet, and 450 nm to blue—700 nm distinctly marks the boundary where red light is prevalent, reinforcing its classification within the visible spectrum. Thus, 700 nm is an accurate wavelength for representing red light.