Electromagnetic Waves PDF

8.4 Electromagnetic Waves (page 422) We are going to learn  What makes up an electromagnetic wave?  How can you model electromagnetic wave behavior?  What kind of waves make up the electromagnetic spectrum? Characteristics of Electromagnetic Waves:  An electromagnetic waves is mad...

8.4 Electromagnetic Waves (page 422) We are going to learn  What makes up an electromagnetic wave?  How can you model electromagnetic wave behavior?  What kind of waves make up the electromagnetic spectrum? Characteristics of Electromagnetic Waves:  An electromagnetic waves is made up of vibrating electric and magnetic fields that can move through space at the speed of light.  The energy that electromagnetic waves transfer through matter or space is called electromagnetic radiation.  Electromagnetic wave do not require a medium such as air, they can transfer energy through a vacuum. Characteristics of Electromagnetic Waves:  Radar is a technology that uses microwaves, a type of electromagnetic wave, to detect objects in the atmosphere.  The vessel is the U.S. Navy’s attempt at using stealth technology to deflect radar.  It’s angular surface causes the microwave to deflect away from the radar source.  Models of electromagnetic Wave Behavior:  An electromagnetic wave consists of vibrating electric and magnetic fields.  Fields are right angle to each other. Wave Model of Light:  The wave theory of light is a scientific theory that describes light as an electromagnetic wave propagating through space.  The theory was first proposed by Christian Huygens in the 17th century and later refined by James Clerk Maxwell in the 19th century.  Christian Huygens in 1690 suggested that light travels in longitudinal waves similar to sound waves in air.  Later, the existence of such a medium was distracted due to inherent contradictions. Wave Model of Light:  Fresnel and Young showed that light propagates as a transverse wave. This theory successfully explained the reflection, refraction, interference, diffraction, and polarization of light waves.  according to Maxwell's EM wave theory , light waves are related to changing electric fields and magnetic fields. The change within the electrical and magnetic field leads to the propagation of electromagnetic waves or light waves. Polarization of light:  Polarization of light is a property shown by transverse waves.  The light waves which travel only in a single plane are known as polarized light waves.  The process of transforming unpolarized light waves to polarized light waves is called the polarization of light.  A polarizing filter act as though it has tiny slits align only in one direction.  The slits can be horizontal or vertical.  When light enter the filter, only waves whose vibrating electric fields are oriented in the same direction as the slits can pass through it.  The light that can pass through it called polarized light. Polarization of light:  Polarized sunglasses block out some waves of light so that ours eyes are not exposed to as much radiation. Particle Model of Light:  The wave model of light does not explain all its properties.  The photoelectric effect is a phenomenon in which electrons are ejected from the surface of a metal when light is incident on it.  Photoelectric effect can be explained by thinking of light of a stream of tiny packets, of energy instead of as a wave.  Each packet of light energy is called a photon.  Particle Model of Light:  One property of light that the wave model explains but the particle model does not is diffraction. Wavelength and Frequency:  According to the wave model for electromagnetic waves.  The waves have all of the properties, that mechanical waves do.  All electromagnetic waves travel at the same speed in a vacuum, but they have different wavelength and different frequency.  Radio waves, which have the longest wavelengths.  Microwaves; infrared; visible light; ultraviolet; x-rays; and finally gamma rays, which have the shortest wavelengths.  Each has properties that make it more useful for some purposes than for some others. Wavelength and Frequency: The Electromagnetic Spectrum:  The complete range of electromagnetic waves placed in order of increasing frequency is called the Electromagnetic spectrum. The Electromagnetic Spectrum:  The electromagnetic spectrum id made up of radio waves, microwaves, infrared rays, visible light, ultraviolet rays, X- rays, and gamma rays.  Radio waves:  A radio wave has a much longer wavelength than visible light. Humans use radio waves extensively for communications. This radio tower has both rectangular and circular antennas to transmit and receive radio frequency energy that connects mobile phones to each other, to the internet and other network. The Electromagnetic Spectrum:  Microwaves:  Microwaves have shorter wavelengths and higher frequency than radio waves. Microwaves are used to detect speeding cars and to send telephone and television communications. But the most common consumer use of microwave energy is in microwave ovens. Microwave radiation include medical imaging technology, GPS technology, and Bluetooth devices. The Electromagnetic Spectrum:  Infrared rays: are electromagnetic waves with wavelength shorter than those of microwaves.  One of the most common uses of infrared radiation is in heat-sensitive thermal imaging cameras. These can be used to study human and animal body heat patterns, but more often, they are used as night-vision cameras.  infrared (IR) light is used by electrical heaters, cookers for cooking food, short-range communications like remote controls, optical fibers, security systems and thermal imaging cameras which detect people in the dark. The Electromagnetic Spectrum:  Visible light: electromagnetic waves that can you see are called visible light.  Visible light waves have shorter wavelengths and higher frequency than infrared rays. The Electromagnetic Spectrum:  Ultraviolet rays: electromagnetic waves with wavelengths just shorter than those of visible light are called ultraviolet rays (UV).  UV rays have high frequency than visible light and carry more energy.  Uses for UV light include getting a sun tan, detecting forged bank notes in shops, and hardening some types of dental filling. They can be used to kill microbes. The Electromagnetic Spectrum:  X-rays:  Electromagnetic waves with wavelengths shorter than those of UV rays are x-rays.  Because of their high frequencies, x-rays carry more energy than UV rays and can penetrate most matter.  X-ray radiography: Detects bone fractures, some types of injuries, calcifications(like kidney stone), and dental problems. The Electromagnetic Spectrum:  Gamma Rays: electromagnetic waves with the shortest wavelength and highest frequencies are gamma rays.  They have the greatest amount of energy of all electromagnetic waves.  Gamma rays are dangerous but do have beneficial uses.  sterilize medical equipment.  Sterilize food.  scan our bodies, see what is happening inside volcanoes, and they are even used to find out if there are any cracks in buildings and bridges.  Radio Therapy- Killing cancer cells.