Electromagnetic Spectrum





Each of these colors actually corresponds to a different wavelength of light.










White light may be separated into its spectral colors by dispersion in a ...












Electromagnetic Spectrum - What is it?

The electromagnetic spectrum is more familiar to you than you might think. The microwave you use to heat your food and the cell phones you use are part of the Electromagnetic Spectrum. The light that our eyes can see is also part of the electromagnetic spectrum. This visible part of the electromagnetic spectrum consists of the colors that we see in a rainbow - from reds and oranges, through blues and purples.


Radiation is energy that spreads out as it is moving.


Electromagnetic spectrum




Wave Lengths


Visible light

Visible light may be defined as any radiation capable to act upon the retina of the human eye causing a visual sensation.

Each simple radiation differs from others by its frequency, i.e. its wavelength.
The representation of a radiation by its wavelength is generally accepted, because the wavelength can be measured with great accuracy.

The graphical representation of a spectrum of electromagnetic radiation is also based on wavelengths.
The visible part of the spectrum spans the relatively narrow range between 380nm and 780nm.

These limits represent experimentally obtained averages, because, in reality, they may vary from one individual to another.



Visible Spectrum

The EM spectrum ranges from gamma rays, which have a very short wavelength and very high energy, to radio waves, which have a very long wavelength and very low energy. Visible light makes up a very small portion of the spectrum.

Image Visible Spectrum Waves

A comparison of light waves and their formal properties.

White light is dispersed by a prism into the colors of the optical spectrum.


The Range and Limits of Human Visual Perception


Visible Spectrum - How do we perceive Color?

As humans, our color vision influences everything from our art and poetry to the colors we paint our homes and the clothing we choose to buy. Yet, we rarely question the mechanics of our color perception – or what we may not be able to see.

How do we perceive color?

We perceive color when the different wavelengths composing white light are selectively interfered with by matter (absorbed, reflected, refracted, scattered, or diffracted) on their way to our eyes, or when a non-white distribution of light has been emitted.

Visible light is merely a small part of the full electromagnetic spectrum, which extends from cosmic rays at the highest energies down through the middle range (gamma rays, X- rays, the ultraviolet, the visible, the infrared, and radio waves) all the way to induction-heating and electric-power-transmission frequencies at the lowest energies. Note that this is the energy per quantum (photon if in the visible range) but not the total energy; the latter is a function of the intensity in a beam.


We can detect the range of light spectrum from about 400 nanometers (violet) to about 700 nanometers (red). We perceive this range of light wavelengths as a smoothly varying rainbow of colors, otherwise known as the visual spectrum.



The Colors of the Visible Light Spectrum

Color Wavelength interval Frequency Interval
red ~ 700–635 nm ~ 430–480 THz
orange ~ 635–590 nm ~ 480–510 THz
yellow ~ 590–560 nm ~ 510–540 THz
green ~ 560–490 nm ~ 540–610 THz
blue ~ 490–450 nm ~ 610–670 THz
violet ~ 450–400 nm ~ 670–750 THz







Waves in the Electromagnetic Spectrum vary in size from very long radio waves the size of buildings, to very short gamma-rays smaller than the size of the nucleus of an atom.








Electromagnetic Spectrum Basics  ( 30 mins)

 An Introduction to the Electromagnetic Spectrum ( EMS)


Electromagnetism is all around us in world in which we live. - We rely on electromagnetic waves to heat our food, carry cell phone calls, and even bring music to the radios in our cars. NASA uses this energy to study vegetation on Earth, monitor solar eruptions on the Sun and detect elements on another planet.


Electromagnetic Radiation:

  •  -  Gamma Rays ( Short)

  •  -  X - Rays

  •  -  Ultraviolet Rays

  •  -  Visible Light Waves

  •  -  Infrared Waves

  •  -  Microwaves

  •  -  Radio Waves

Images courtesy of NASA




Book & DVD






To tour the electromagnetic spectrum, follow the links below! ( For Students)



Tour of the Electromagnetic Spectrum - NASA









Infrared <> Visible Light Comparison in Astronomy


Fastest Stuff in the Universe: The Electromagnetic Spectrum

What goes at the speed of light?


 Well, a few different things actually. The Electromagnetic Spectrum is the group of types of radiation that goes at the speed of light. These types pf radiation are also known as waves. When high energy objects move at high speeds through space, they give off these electromagnetic waves. The most unique characteristic of these waves is the way it travels. Electromagnetic Waves are the only waves that do not need a medium, also known as molecules to travel through. They can travel through a vacuum.....









EMS Microwave used on Doppler Radar


 Different wavelengths of microwaves produce different information for scientists to use. C-band microwaves go through clouds, dust, smoke, snow, and rain to reveal the Earth's surface which then can help weather men.


L-band microwaves, which are the ones used by a GPS in your car, can also go through the canopy cover of forests to measure the soil moisture of rain forests.










A magnet levitating above a superconductor cooled by liquid nitrogen.


Diagram of the Meissner effect. Magnetic field lines, represented as arrows, are excluded from a superconductor when it is below its critical temperature.



Meissner effect


The Meissner effect is an expulsion of a magnetic field from a superconductor during its transition to the superconducting state. The German physicists Walther Meissner and Robert Ochsenfeld discovered the phenomenon in 1933 by measuring the magnetic field distribution outside superconducting tin and lead samples.[1] The samples, in the presence of an applied magnetic field, were cooled below their superconducting transition temperature. Below the transition temperature the samples cancelled nearly all interior magnetic fields. They detected this effect only indirectly; because the magnetic flux is conserved by a superconductor, when the interior field decreased, the exterior field increased. The experiment demonstrated for the first time that superconductors were more than just perfect conductors and provided a uniquely defining property of the superconducting state.






The Meissner Effect  ( 4  mins)


This is a little experiment to illustrate the Meissner effect in a superconductor.
It was performed at the University of Twente in Enschede, The Netherlands, under the supervision of Prof. Alexander Brinkman.













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