Week 8 Electromagnetic Waves PDF

WEEK 8 ELECTROMAGNETIC WAVES  DISCOVERY  PROPERTIES  Types of Electromagnetic Radiation TERMINOLOGIES Propagation - The act or process of propagating, especially the process by which a disturbance, such as the motion of electromagnetic or sound waves, is transmitted through a medium su...

WEEK 8 ELECTROMAGNETIC WAVES  DISCOVERY  PROPERTIES  Types of Electromagnetic Radiation TERMINOLOGIES Propagation - The act or process of propagating, especially the process by which a disturbance, such as the motion of electromagnetic or sound waves, is transmitted through a medium such as air or water. Spectrum - the arrangement according to the wavelength of visible, ultraviolet, and infrared light. Electromagnetic radiation - the flow of energy at the universal speed of light through free space or through a material medium in the form of the electric and magnetic fields that make up electromagnetic waves. Discovery of Electromagnetic Waves JAMES CLERCK MAXWELL His discovery is first commented on. Maxwell had proved that light was an electromagnetic wave. In 1865 Maxwell wrote down an equation to describe these electromagnetic waves HEINRICH HERTZ Heinrich Hertz demonstrated the generation and detection of radio waves in 1887, eight years after Maxwell’s death. Hertz also showed that these waves travel at the speed of light (as predicted by Maxwell). PROPERTIES of ELECTROMAGNETIC WAVE 1. Transverse waves Both fields are perpendicular to the propagation direction 2. Light is an Electromagnetic 4. Electromagnetic waves carry wave energy and momentum An electromagnetic wave, although it The value of the speed of light is carries no mass, does carry energy. It 3 × 108 m/s is also the value of an also has momentum and can exert electromagnetic wave. pressure (known as radiation pressure). 3. Can travel through a vacuum 5. They obey the equation c = fλ. Because of the existence of Here, f is the frequency in Hertz and λ is electric and magnetic fields in a the wavelength meters. The product of vacuum wavelength and frequency is equal to a constant c, the speed of light which is equal to 3 × 108 m/s.  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 1. Frequency – measured in Hertz (Hz); radio waves and microwaves 2. Wavelength – measured in wavelength (meters); infrared rays and visible light 3. Energy – measured in electron Volts (eV) ; x-rays and gamma rays  TYPES of ELECTROMAGNETIC RADIATION ELECTROMAGNETIC RADIATION the flow of energy at the universal speed of light through free space or a material medium in the form of the electric and magnetic fields that make up electromagnetic waves. RADIO WAVES Radio waves are at the lowest range of the EM spectrum. Radio is used primarily for communications including voice, data, and entertainment media. MICROWAVES Microwaves fall in the range of the EM spectrum between radio and IR. used for high-bandwidth communications, radar, and as a heat source for microwave ovens and industrial applications. INFRARED RADIATION (IR) Infrared is in the range of the EM spectrum between microwaves and visible light. IR light is invisible to human eyes, but we can feel it as heat if the intensity is sufficient. Commonly used as heat sensors VISIBLE LIGHT Visible light is found in the middle of the EM spectrum, between IR and UV. defined as the wavelengths that are visible to most human eyes.. ULTRAVIOLET Ultraviolet light is in the range of the EM spectrum between visible light and X-rays. UV light is a component of sunlight; however, it is invisible to the human eye. It has numerous medical and industrial applications, but it can damage living tissue. X-RAYS X-rays are roughly classified into two types: soft X-rays and hard X-rays. Soft X-rays comprise the range of the EM spectrum between UV and gamma rays. Hard X-rays occupy the same region of the EM spectrum as gamma rays. The only difference between them is their source: X-rays are produced by accelerating electrons, while gamma rays are produced by atomic nuclei. GAMMA RAYS Gamma rays are in the range of the spectrum above soft X-rays. Gamma radiation causes damage to living tissue, which makes it useful for killing cancer cells when applied in carefully measured doses to small regions. Uncontrolled exposure, though, is extremely dangerous to humans