The Electromagnetic Spectrum

By

Katie Markham

Visible Light

• There is a very small section of the electromagnetic spectrum that the human eye can perceive. It is known as the visible color spectrum, or what most refer to as the rainbow. The colors that we, here on earth, label as black are actually what make up the rest of the spectrum.

Perception

• The section that the human eye is able to perceive starts around 400nm (blue) and ends around 700nm (red). Of course every persons perception is different.

The Rainbow

• Just as in most other things the electromagnetic spectrum has a unit of measure, nanometers among others. Similar to the rainbow that we know the visible color spectrum starts as “red” and end as “blue”. What proceeds that is the imperceptible to us such as, infrared, ultra violet, micro waves, x-rays, radio, and gamma waves.

Radio Waves and Astronomy• One of the most important advances in

astronomy was the radio telescope. It allows scientists to discover other galaxies, planets, and stars without the use of the human eye. These telescopes are designed to pick up strong signals or radio waves, which make it possible to study other galaxies.

Radio Transmission

• As previously stated, the electromagnetic spectrum has many measurements. Our atmosphere, here on earth, is only able to emit certain parts of the spectrum. Radio waves are un-seeable to the human eye but are what is used for electronic communication.

Microwaves

• Scientist theory of “The Big Bang” is strongly supported by microwave evidence. In astronomy they have a specific term for this radiation called CMB or Cosmic Microwave Background. Using this they can go back and find out what really happened with the gigantic shockwave. They are also used in our microwaves to super heat food. Once again they are invisible to the human eye.

Infrared Radiation• Infrared radiation is mostly derived from

massive amounts of heat. Like radio waves, satellites have been sent in to space to pick up radiation caused by heat and rapid movement of molecules and atoms. The European Space Agency (ESA) has an entire Infrared Space Observatory which mainly focuses on “dusty regions on space”. These regions are easily studied with today’s technology and satellites.

Ultra Violet Radiation

• This type of radiation is one of the closest to visible light and is on the blue end of the spectrum. With the assistance of explorers data can be collected using ultra violet rays. Temperature, distance, and composition of objects and places in space can all be determined. Ultra Violet radiation is not emitted into our atmosphere, and it is also invisible to us.

X-rays

• X- ray are useful to study things with high energy levels. There are specific stars called Neutron Stars that are easily seen using x ray technology. These stars are located around black holes therefore producing massive amounts of energy. This is the same radiation that doctors use to in vision broken bones.

Gamma Rays

• Objects containing even more energy are amounted using gamma rays. So in a sense they are their own unit of measure. With the development of Compton Scattering these rays can be very accurately measured. Basically what that is a theory that some objects molecules can in fact interact with gamma rays.

Spectroscopes• The Main job or spectroscopes is to separate

the different colors of light generating off of stars. The way that they work is by having light travel through a lens. Then be refracted though a prism. After that it travels through another lens, once again being refracted. Finally the light is transposed on to a photographic plate. Spectroscopes allow astronomers to see chemical composition of atmospheres, pressure, magnetic field and temperature of stars. Distances can also be concluded.

The After Math

• The product of these scopes are three different types of visible spectra. All within the visible light spectrum. They are; the continuous spectrum, the bright- line spectrum, and the dark- line spectrum.

Continuous Spectrum

• There are three materials that this is able to see. Both glowing liquids and solids and the super hot gases compressed in a star.

Bright- Line Spectrum

• The way it is projected this spectra looks like a bunch of separated lines. This part is designed to only show some types of brightly colored lines. Chemical gas and vapor clouds are what causes this spectrum. Apparently each element has its own specific bright- line spectrum.

Dark- Line Spectrum

• Like the bright- line spectrum this one also absorbs light from elements. But, the way it interprets the light after it has traveled through a cooler gas than it had been traveling in. The way to find out what particular gas the wavelengths traveled though is that, every gas absorbs the exact same amount of wave lengths if it were heated. Every gas has different wave length absorption.

Spectra in the Stars• With the combined help of the bright and

dark line spectrum scientists develop atmospheric compositions of far of starts and planets. Some planets however, do not contain gases that show up using spectra scopes. Scientists at first were puzzled by this, until they managed to draw the conclusion that their atmosphere are made of unknown gases to us, because our atmosphere doesn’t contain them.

Colors of Stars

• Just by looking up at the sky you can tell which are the hotter and which are the colder stars. Likewise to a camp fire the hottest stars are a blue-ish white color, and the cooler ones are of a red shade. ROYGBIV (red, orange, yellow, blue, indigo, violet) is the basic order from coolest to hottest stars. These clues also help astronomers determine the chemical composition of the stars.

The Doppler Effect• This is used to describe many things in the

electromagnetic spectrum. It deals mostly with blue and red shifts. When frequency appears to increase it is called a blue shift. But when it is drawn away or decreases it is called a red shift. Astronomers mainly study this shift in stars, galaxies and clouds. The shift is really the difference between frequency and wave length.

• http://sci2.esa.int/interactive/media/flashes/2_2_1.htm

Doppler Effect Cont.

• There are several classifications of red shifts. Gravitational Redshifts are when change is radiation is thought to be to large gravitational fields. Cosmological Redshifts are related to “The Big Bang” and the continues expansion of space. Not only is this effect witnessed in out side of the ozone, it is also here on earth.

The Doppler Effect on Earth

• On Earth the most commonly sighted or rather heard Doppler Effect is within sound frequencies, such as the path of an ambulance. The sound of he siren seems to change frequencies so that is the lengthening and shortening of the sound waves as they are shot off of other objects. This theory was presented by Christian Doppler a mathematician and physicist.

Bibliography

• Doppler Effect. http://sci2.esa.int/interactive/media/flashes/2_2_1.htm

• Electromagnetic Spectrum. http://en.wikipedia.org/wiki/Electromagnetic_spectrum. June 2006

• Science Discoveries Isaac Newton and Gravity. Chelsea House Publishers.12-13

• Spaulding, Nancy E., and Samuel N. Namowitz. Earth Science. Evanston Illinois: McDougal Littell, 1994. 370-375.