Which of the following is an example of an electromagnetic wave?
a. red light
b. ocean waves
c. sound waves
d. earthquakes

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:

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.

the working equation for the angular size is the product of the physical size and 360 degrees divided by the product of two pi and distance from earth. the minimum size would be 0.559 degrees while the maximum size would be 0.49 degrees. 

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