The Electromagnetic Spectrum

Electromagnetic Waves 1. Stars send energy called electromagnetic waves into space. a. Unlike other types of waves, electromagnetic waves travel through empty space. b. The kind of energy that electromagnetic waves carry is called radiant energy. 2. The electromagnetic spectrum is the entire range of energy carried by electromagnetic waves. a. The shortest electromagnetic waves are called gamma rays. b. The longest electromagnetic waves are called radio waves. c. Humans can directly observe a small part of the electromagnetic spectrum, which is called visible light.

3. The amounts of different types of radiant energy stars emit vary from star to star, depending on the temperature of the star. a. Hot stars emit most of their radiant energy as short electromagnetic waves, such as gamma rays and X-rays. These waves have higher energy. b. Cool stars emit most of their radiant energy as long electromagnetic waves with low energy, such as radio waves and infrared waves.

4. Planets and moons do not emit their own light. Instead, they reflect light from the Sun. That is the reason we can see these objects in the sky. 5. All light waves travel at 300,000 km/s, which is called the speed of light.

What is the electromagnetic spectrum? The electromagnetic spectrum consists of all the different wavelengths of light (also known as electromagnetic radiation), including visible light, radio waves, and X-rays. Light is a continuum of wavelengths. We name regions of the spectrum a bit arbitrarily, but the names give us a general sense of the energy; for example, infrared light has shorter wavelengths than radio light. The only region in the entire electromagnetic spectrum that our eyes are sensitive to is the visible region.

Wavelength and frequency Light is measured by its wavelength (in nanometers) or frequency (in Hertz). One wavelength equals the distance between two successive wave crests or troughs. Nanometer - A very small fraction of a meter. There are a billion (1,000,000,000) nanometers (nm) in one meter Frequency (Hertz) equals the number of waves that passes a given point per second.

Wavelength, Frequency and Energy Short wavelength = high frequency = high energy Long wave length = low frequency = low energy

Gamma rays Gamma rays have the shortest wavelengths, < nanometers (about the size of an atomic nucleus). This is the most energetic region of the electromagnetic spectrum. Gamma rays can result from high-energy reactions taking place in objects such as pulsars, quasars, and black holes.

X-rays X-rays range in wavelength from 0.001–10 nanometers (about the size of an atom). They are generated, by superheated gas from exploding stars and quasars, where temperatures can reach more than 10 million degrees Celsius.

Ultraviolet Radiation Ultraviolet radiation has wavelengths of 10– 400 nanometers (about the size of a virus). Young, hot stars produce a lot of ultraviolet light that bathes interstellar space with this energy and causes nearby gas to glow as nebulae.

Visible light Visible light covers the range of wavelengths from 400–700 nanometers (from the size of a molecule to a protozoan). Our Sun emits most of its radiation in the visible range, which our eyes perceive as the colors of a rainbow. Our eyes are sensitive only to this small portion of the electromagnetic spectrum. ROY G BIV Visible light covers the range of wavelengths from 400–700 nanometers (from the size of a molecule to a protozoan). Our Sun emits most of its radiation in the visible range, which our eyes perceive as the colors of a rainbow. Our eyes are sensitive only to this small portion of the electromagnetic spectrum. ROY G BIV Red Orange Yellow Green Blue Indigo Violet

Infrared wavelengths Infrared wavelengths span from 700 nanometers – 1 millimeter (from the width of a pinpoint to the size of small plant seeds). Infrared radiation is associated with heat. At a temperature of 98.6 degrees Fahrenheit (37 degrees Celsius), our bodies radiate with a peak intensity near 900 nanometers.

Microwaves Microwaves have wavelengths between 1 millimeter and 1 meter. The radiation resulting from the "big bang" is detected in the microwave region and is often referred to as the microwave background radiation. Microwave ovens use a specific microwave frequency to cause water molecules to absorb the energy and thus heat food.

Radio Waves Radio waves are longer than 1 meter. Because these are the longest waves, they have the lowest energy and are associated with the lowest temperatures. Radio wavelengths are found many places: in a variety of stars (especially binary, X-ray, and other active stars), in interstellar clouds, in pulsars, and in the cool remnants of supernova explosions. Radio stations use radio wavelengths to send signals that our radios then translate into sound.

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