PowerPoint Presentation: E lectromagnetic waves PowerPoint Presentation: Light, microwaves, x-rays, and TV and radio transmissions are all kinds of electromagnetic waves. What are electromagnetic waves ? PowerPoint Presentation: An electromagnetic wave is an energy wave produced from an electrical discharge. Electromagnetic waves have rise and fall cycles. The number of rise and fall cycles per second is its frequency. We can’t see or feel them, but they are around us. PowerPoint Presentation: Interrelated electric and magnetic fields traveling through space All electromagnetic radiation travels at c = 3 10 8 m/s in vacuum – the cosmic speed limit! real number is 299792458.0 m/s exactly Electromagnetic Radiation Different types of waves: Different types of waves Radio Waves-longest wavelength. AM/FM, TV Microwaves- 2nd longest wavelength. Radar, Microwaves Infrared Waves- 3rd longest wavelength. Infrared photography, night vision Visible Light- 4th longest wavelength. Microscope, astronomy Ultraviolet Light- 5th longest wavelength. Sterilization X Rays- 6th longest wavelength. Medical exam of teeth and bones Gamma Rays- Shortest wavelength. Used in cancer treatment and food irradiation PowerPoint Presentation: What distinguishes these from one another? PowerPoint Presentation: When you listen to the radio, watch TV, or cook dinner in a microwave oven, you are using electromagnetic waves. Radio waves, television waves, and microwaves are all types of electromagnetic waves. They differ from each other in wavelength. Wavelength is the distance between one wave crest to the next. History: History In the 1860's and 1870's, a Scottish scientist named James Clerk Maxwell developed a scientific theory to explain electromagnetic waves. He noticed that electrical fields and magnetic fields can couple together to form electromagnetic waves. He summarized this relationship between electricity and magnetism into what are now referred to as "Maxwell's Equations." PowerPoint Presentation: Heinrich Hertz, a German physicist, applied Maxwell's theories to the production and reception of radio waves. The unit of frequency of a radio wave -- one cycle per second -- is named the hertz, in honor of Heinrich Hertz. His experiment with radio waves solved two problems. First, he had demonstrated in the concrete, what Maxwell had only theorized — that the velocity of radio waves was equal to the velocity of light! This proved that radio waves were a form of light! Second, Hertz found out how to make the electric and magnetic fields detach themselves from wires and go free as Maxwell's waves — electromagnetic waves. PowerPoint Presentation: Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. This diagram shows a plane linearly polarized wave propagating from left to right. The electric field is in a vertical plane and the magnetic field in a horizontal plane. Properties of the Electromagnetic waves : : Properties of the Electromagnetic waves : Electromagnetic Wave- A transverse wave consisting of oscillating electric and magnetic fields at right angles to each other. The spectrum includes more than visible light- not all light is visible to the human eye . Light is a wave and also a particle PowerPoint Presentation: Electromagnetic waves are formed by the vibrations of electric and magnetic fields. These fields are perpendicular to one another in the direction the wave is traveling. Once formed, this energy travels at the speed of light until further interaction with matter. DESCRIBING ELECTROMAGNETIC ENERGY : DESCRIBING ELECTROMAGNETIC ENERGY The terms light, electromagnetic waves, and radiation all refer to the same physical phenomenon: electromagnetic energy. This energy can be described by frequency, wavelength or energy. All three are related mathematically such that if you know one, you can calculate the other two. Radio and microwaves are usually described in terms of frequency (Hertz), infrared and visible light in terms of wavelength (meters), and x-rays and gamma rays in terms of energy (electron volts). This is a scientific convention that allows the convenient use of units that have numbers that are neither too large nor too small. FREQUENCY: FREQUENCY The number of crests that pass a given point within one second is described as the frequency of the wave. One wave—or cycle—per second is called a Hertz (Hz), after Heinrich Hertz who established the existence of radio waves. A wave with two cycles that pass a point in one second has a frequency of 2 Hz. Frequencies for different colors: Frequencies for different colors Every electromagnetic wave exhibits a unique frequency, and wavelength associated with that frequency. For instance, this picture represents an electromagnetic wave corresponding to the color red. Its frequency is 428 570 GHz (pronounced gigahertz), which can also be stated as 428,570 billion cycles per second. So when you look at red light, your eye receives over four hundred trillion waves every second! PowerPoint Presentation: Visible light waves are the only electromagnetic waves we can see. We see these waves as the colors of the rainbow. Each color has a different wavelength. Red has the longest wavelength and violet has the shortest wavelength. When all the waves are seen together, they make white light. When white light shines through a prism, the white light is broken apart into the colors of the visible light spectrum. Water vapor in the atmosphere can also break apart wavelengths creating a rainbow. Cones in our eyes are receivers for these tiny visible light waves. The Sun is a natural source for visible light waves and our eyes see the reflection of this sunlight off the objects around us. The color of an object that we see is the color of light reflected. All other colors are absorbed. Visible Spectrum : : Visible Spectrum : Visible Spectrum ROYGBIV= Red, Orange,Yellow , Green, Blue, Indigo, Violet Microwaves: Microwaves Microwaves have wavelengths that can be measured in centimeters! The longer microwaves, those closer to a foot in length, are the waves which heat our food in a microwave oven. Microwaves are good for transmitting information from one place to another because microwave energy can penetrate haze, light rain and snow, clouds, and smoke. Because microwaves can penetrate haze, light rain and snow, clouds and smoke, these waves are good for viewing the Earth from space. X-Rays: X-Rays When you get an X-ray taken at a hospital, X-ray sensitive film is put on one side of your body, and X-rays are shot through you. Because your bones and teeth are dense and absorb more X-rays then your skin does, silhouettes of your bones or teeth are left on the X-ray film while your skin appears transparent. Many things in space emit X-rays, among them are black holes, neutron stars, binary star systems, supernova remnants, stars, the Sun, and even some comets! WAVELENGTH: WAVELENGTH Electromagnetic waves have crests and troughs similar to those of ocean waves. The distance between crests is the wavelength. The shortest wavelengths are just fractions of the size of an atom, while the longest wavelengths scientists currently study can be larger than the diameter of our planet! ENERGY: ENERGY An electromagnetic wave can also be described in terms of its energy—in units of measure called electron volts ( eV ). An electron volt is the amount of kinetic energy needed to move an electron through one volt potential. Moving along the spectrum from long to short wavelengths, energy increases as the wavelength shortens. Consider a jump rope with its ends being pulled up and down. More energy is needed to make the rope have more waves.