“Characteristics of Light” and “Electromagnetic Waves” Travis Zelfer Mrs. Grayot—Physics—6th hour 3/1/2009 Alternative Assessment

Two Theories Used to explain the characteristics of light. Quantum theory: the quantum theory of light applies to X-ray, radiation, and photoelectricity. This theory states that light is a steady stream of high-speed particles and that all light sources send out a stream of these particles. Each particle of light is referred to as a photon. Wave Motion theory: The wave motion theory of light involves reflection, absorption, transmission, and polarization of light.

Characteristics Light is a electromagnetic radiation. Light is also an electromagnetic wave. Not all light is visible to the human eye Electromagnetic radiation that is visible to the human eye, from 380 to 770 nanometers. Form of energy. Light striking an object is either absorbed or reflected.

Things to know LIGHT:  Light  stimulates  the  perception  of  sight.  White  light  is  made  of equal intensities of all wavelengths within the visible spectrum. WAVELENGTH:   the chief determinant of perceived color. A wavelength is defined as the distance from the crest of one wave to the crest of the next wave. Wavelengths are measured in nanometers (nm) which are equal to one millionth of a millimeter.    Light travels in a straight line, and when it encounters an object or enters a new medium. SPEED:    The speed of light is constant until it passes through a new medium, such as water, air, or glass. The speed of light is the product of wavelength multiplied by the frequency. Dividing the frequency by the constant speed of light results in approximate wavelength. FREQUENCY:  Frequency  is  the  number  of  wavelengths  passing  a  given point in 1 second.

Characteristics of Electromagnetic Waves Transverse waves, similar to water waves in the ocean or the waves seen on a guitar string. All waves have amplitude, wavelength, velocity and frequency. Travel at the speed of light. The spectrum of their wavelengths results in waves that are used in many useful devices. They are formed by heat, electronics, and nuclear forces. Electromagnetic waves are created by the acceleration or oscillation of electrical charges, such as the movement of electrons.

Electromagnetic Waves Radio waves, microwaves, x-rays, and even visible light are all waves of energy called electromagnetic waves. They are all part of the electromagnetic spectrum with a different range of wavelengths which cause waves to affect matter differently. The creation and detection of the wave depend much on the range of wavelengths.

Approximate frequency range Approximate wavelength range Application Approximate frequency range Approximate wavelength range AC electricity 50-60 Hz 6000-5000 km AM radio 106 Hz 300 m FM radio and TV 108 Hz (100 MHz) 3 m Radar 1010 Hz 3 cm Microwaves 1011 Hz 3 mm Infrared 3*1011 - 4*1014 Hz 1 mm - 700 nm Visible light 4*1014 - 7.5*1014 Hz 700 - 400 nm Ultraviolet 1016 Hz 400 nm - 10 nm X-rays 1018 Hz 10 nm - 0.1 nm Gamma rays 1019 Hz 0.03 nm

What is the Electromagnetic Spectrum? The electromagnetic spectrum is the range of frequencies or wavelengths of electromagnetic radiation. It includes x-rays, visible light, microwaves and television waves. The rate of oscillating movement of electrical charges determines the frequency of electromagnetic radiation. c = f x λ c = the speed of light f = the frequency of the electromagnetic wave λ =the wavelength of the electromagnetic wave

Electromagnetic Spectrum The range of wavelengths for electromagnetic waves--from the very long to the very short--is called the Electromagnetic Spectrum: Radio and TV waves are the longest usable waves, having a wavelength of 1 mile or more. Microwaves are used in telecommunication as well as for cooking food. Infrared waves are barely visible. They are the deep red rays you get from a heat lamp. Visible light waves are the radiation you can see with your eyes. Their wavelengths are in the range of 1/1000 centimeter. Ultraviolet rays are what give you sunburn and are used in "black lights" that make object glow. X-rays go through the body and are used for medical purposes. Gamma rays are dangerous rays coming from nuclear reactors and atomic bombs. They have the shortest wavelength in the electromagnetic spectrum of about 1/10,000,000 centimeter.

Prism

Explanation As light enters the prism, light bends down. The bending occurs because the light travels faster through the air than it does through the prism. When the lower part of the wave enters the prism, it slows down. Since the upper portion of the wave is still traveling faster than the lower portion, it causes the wave to bend. As the wave exits the prism, the upper portion exits first and begins travelling faster than the lower portion hat is still in the prism. When light hits a prism at certain angles, the light will refract , causing it to be separated into its individual frequencies. This effect occurs because of the shape of the prism and the angle of the light.

The End Presented By: Travis Zelfer Lab and worksheet to follow.