Question

Which color of light has a wavelength of 5.0x10^-7 meters in air?

Answer 1

Green light.

In fact, wavelength of $5\cdot 10^{-7} m$ corresponds to 500 nm. The spectrum of visible light goes from approximately 380 nm (corresponding to violet light) to 750 nm (corresponding to red light). Green is approximately in the middle, having a wavelength range between 495-570 nm, therefore 500 nm lies in this range.