# LIGHT WAVELENGTH SIZE

Objective: Match the Size of Different Light Wavelengths with the Sizes of Familiar Objects

Light Gives Us Information About Objects in Space:
Light provides us with information about objects in the universe. For example, by studying infrared light from a nebula, we can tell how hot its gases are. By studying extreme ultraviolet light from a white dwarf star we can study what materials it is made of. So, by studying the entire electromagnetic spectrum (all the different types of light), scientists have been able to discover that the universe is a far more vibrant environment than the eye can see. Data gathered in non-visible wavelengths allows both a better understanding of known objects and the discovery of new objects, such as gamma-ray bursters that radiate all their energy outside the range of visible light.

But How Do Astronomers Decide What Type of Light is Coming from these Objects in Space?
Different types of light differ in wavelengths (remember, this is the distance from the peak to peak or trough to trough of a wave). For example, the wavelength of extreme ultraviolet light may measure 100 angstroms, visible light has wavelengths that range from about 4,000 to 7,000 angstroms. How long is 100 angstroms or 4,000 angstroms? And just what is an "angstrom?" Keep on reading and find out!

How Long Is An Angstrom?
Astronomers use a tiny unit of distance called the "angstrom" to measure wavelengths. Angstroms are abbreviated " Å" and named after the Swedish physicist A.J. Angstrom. One angstrom equals .00000001 cm, a very tiny length. That means that visible light may have a wavelength of 4,000 angstroms or about .00004 cm. One angstrom is pretty small compared to our own body size. But just how small is it? Take a look at the images below. See if you can find the closest object in length to a visible light wavelength.

Test Your Knowledge of Wavelength Size!
Use the tool in the bottom frame to try out your answers

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The length of this C2H6 Molecule , composed of 2 carbon atoms and 6 hydrogen atoms, is about 50 angstroms
(Image courtesy Scott Van Bramer at Widener University)

 What types of light have a wavelength shorter than the length of a C2H6 molecule?
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The length of a red blood cell
is about 80,000 (eighty thousand) angstroms

 How does this compare to your input and LIGHT OUTPUT in the left frame on this page?
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The length of the body of this fly is about 60,000,000 (sixty million) angstroms

 What type of light has a wavelength as long as the body of a fly?
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The length of the wingspan of this butterfly
is about 500,000,000 (five hundred million) angstroms

 Compare this to radio light waves that can have wavelengths longer than 1 meter or 10,000,000,000 angstroms .
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 The length of the diameter of the Earth is about 34,759,930,480,000,000 angstroms or over 34 quadrillion angstroms
 Are there types of light that have wavelengths this long? Hmmm. 34 quadrillion angstroms! It seems that when we are measuring big things the angstrom may not be the most appropriate unit of measurement. This is also true for certain types of light. angstroms work well for short wavelengths of light, such as ultraviolet or visible, but once we start talking about longer wavelengths of light, other units of measurement are more appropriate. Can you think of more appropriate units for measuring the wavelength of infrared, microwave, and radio light waves?

Which of the objects above was closest in length to the wavelength of visible light?

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