Answer:
a. Red light
Explanation:
Red light is part of the electromagnetic waves.
Electromagnetic waves are oscillations of the electric and the magnetic fields in a plane perpendicular to the direction of travelling of the wave.
All electromagnetic waves travel in a vacuum at the same speed, which is known as the speed of light, and its value is:
[tex]c=3.0\cdot 10^8 m/s[/tex]
Electromagnetic waves are classified into 7 different types, according to their wavelength/frequency. From the shortest to the longest wavelength we have the following:
Gamma rays
X rays
Ultraviolet
Visible light
Infrared radiation
Microwaves
Radio waves
Visible light is the only part of the spectrum that the human eye is able to see. Its range of wavelength goes from 380 nm to 750 nm, and we perceive the light at different wavelengths in this region as different colors.
In particular, the visible light with longer wavelength (between 700-750 nm) is perceived by the human eye as red light.
