EMR - Electromagnetic Radiation

The visible light region is part of the electromagnetic spectrum.

(λ)=400 nm
Single Wavelength
(λ)=700 nm
SVG animation of a sine wave.

Electromagnetic waves of energy are a combination of an electric field and a magnetic field that oscillate while traveling at the speed of light. EMR regions are classified by wavelength, largest to smallest: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays.

(λ) is the Greek letter lambda. It is the symbol used to express wavelength.

This mathematical relationship holds true for all electromagnetic waves.

(λ) = c/f   or   f = c/(λ)

(λ), represents a single cycle (period) of EMR (∿) with a length in meters.

c, is the speed of light, in meters per second: 299,792,458 m/s.

f, is the frequency, in cycles per second, expressed in Hertz (Hz).

If 550 nm is the midpoint of the visible light spectrum, what is the frequency at that point?

Answer





Radio Frequency (λ) = 100 m



Microwave (λ) = 10 mm
Microwaves occupy a region of EMR with wavelengths ranging from 1 mm to 1 meter making them short-wavelength radio waves. Microwave ovens radiate at a frequency of 2.45 GHz, with (λ) = 122 mm, creating heat from molecular friction via a transfer of energy. The wave properties of microwaves make them well suited for use in satellite communication and radar systems.


Infrared (λ) = 10 μm
The invisible infrared region covers wavelengths from 700 nm up to 1 mm. IR is also known as thermal radiation and is naturally produced by solar radiation and fire. Every object, both hot and cold, gives off heat in the form of IR. IR has a lower energy level and a longer wavelength than the EMR that produces visible light.


Visible Light (λ) = 550 nm
The visible light spectrum is a very narrow band of the electromagnetic spectrum. Visible light is comprised of the colors of the rainbow: red, orange, yellow, green, blue, indigo, and violet. Different wavelengths correspond to the different colors, with red having the longest wavelength and violet the shortest. Our eyes detect this specific range of wavelengths that the brain interprets as colors. When combined together the visible wavelengths appear as white light.


Ultraviolet (λ) = 100 nm
The invisible ultraviolet region covers wavelengths from 400 nm down to 10 nm. The sun is the major source of UV radiation that is known for it's harmful UV-B and UV-C sub-regions that are mostly absorbed by the earth's atmosphere. UV has a higher energy level and a shorter wavelength than the EMR that produces visible light.


X-rays (λ) = 1 nm
X-rays (χ) are high-energy electromagnetic radiation with wavelengths between 0.01 nm and 10 nm and are generated when inner-shell electrons transition between energy levels. Both X-rays and light waves transport energy as waves and photons. Their short wavelengths allow them to pass through less dense materials but not through dense materials such as bone. X-rays are a high energy form of ionizing radiation, meaning they can damage living tissue.


Gamma rays (λ) = 1x10-6 nm
Gamma rays (γ) are the highest-energy form of EMR and originate from the nucleus of an atom. Gamma rays have the smallest wavelengths and are classified as both a wave, and photons that travel as mass-less packets of pure energy. They are produced by nuclear processes like radioactive decay and supernova explosions. They are highly penetrating, able to pass through dense materials like lead, and can cause damage to living tissue by ionizing atoms.