EM Waves PDF

ELECTROMAGNETIC WAVES  ELECTROMAGNETIC WAVES Electromagnetic waves or EM waves are waves that are created as a result of vibrations between an electric field and a magnetic field.  ELECTROMAGNETIC WAVES Electromagnetic waves or EM waves are t...

ELECTROMAGNETIC WAVES  ELECTROMAGNETIC WAVES Electromagnetic waves or EM waves are waves that are created as a result of vibrations between an electric field and a magnetic field.  ELECTROMAGNETIC WAVES Electromagnetic waves or EM waves are transverse waves. It does not need a medium to travel or propagate. They move at 3 x 108 m/s (speed of light) in a vacuum. JAMES CLERK MAXWELL He predicted the existence of electromagnetic wave. But it was because of Heinrich Hertz, that these were proven.  ELECTROMAGNETIC SPECTRUM Electromagnetic Spectrum is the continuous range of electromagnetic waves arranged in order of frequency or wavelength.  The shorter the wavelength the more frequency. The more frequency a wave has the more energy it emits.  RADIO WAVES These are the longest of all the electromagnetic waves. The frequency of radio waves ranges from 3.0 x 104 to 3.0 x 1012 or 300 to 3000 MHz.  HEINRICH HERTZ It was discovered by Heinrich Hertz in 1887. The sun and Jupiter are extra terrestrial sources of radio waves.  Type of Frequency Frequency Range Common Applications Long-distance communication Low Frequency 30- 300kHz and navigation Amplitude Modulation (AM) radio Medium Frequency 300- 3000 kHz broadcasting Shortwave broadcasting, tags for use in building access, public High Frequency 3-30 MHz transportation and electronic payment system. Frequency Modulation (FM) radio broadcasting, ground-to-aircraft Very High Frequency 30- 300 MHz and aircraft-to-aircraft communication. Police radio communication, military aircraft and television Ultra High Frequency 300- 3000 MHz transmission, modern cell phones and global positioning system (GPS) OTHER APPLICATIONS OF RADIO WAVES Radar (Radio Detection and Ranging) used for detection of objects, weather forecasting, military surveillance and air traffic control, as well as monitoring speed in highway patrol and tracking satellite and debris. OTHER APPLICATIONS OF RADIO WAVES OTHER APPLICATIONS OF RADIO WAVES MEDICAL APPLICATION OF RADIO WAVES  JAMES CLERK MAXWELL These are the longest of all the electromagnetic waves. The frequency of radio waves ranges from 3.0 x 108 to 3.0 x 1011 or 3000 MHz to 300 GHz. James Clark Maxwell is credited for its discovery.  USES OF MICROWAVES Microwaves are high frequency radio waves used for communication. They were mostly used for long distance calls, before the introduction of optical fibers.  USES OF MICROWAVES Microwave oven uses 2.45 GHz microwaves to cook or heat food by transferring energy to the water molecules in the food.  MEDICAL USE OF MICROWAVES Microwave Imaging is used to assess and monitor progress of treatment of breast cancer via microwave tomography.  INFRARED WAVES Infrared literally means “below red”. It has a lower frequency than the red part of visible light. Infrared radiation (IR) has a frequency ranging from 3 x 1011 to 4 x 1014  SIR WILLIAM HERSCHEL Sir William Herschel discovered infrared waves in 1800.  INFRARED WAVES Infrared radiation cannot be seen by the naked eye but can be felt as heat. People, animals, and objects give off infrared radiation proportional to their temperature.  INFRARED WAVES Objects with higher temperature produce infrared rays of shorter wavelengths and higher frequencies than objects with lower temperatures. OTHER APPLICATIONS OF INFRARED WAVES OTHER APPLICATIONS OF INFRARED WAVES MEDICAL APPLICATIONS OF INFRARED WAVES  VISIBLE LIGHT It is the only electromagnetic wave which the human eye can see. Its frequency ranges from 4 x 1014 to 8 x 1014. Its wavelength ranges from 4 x 10-7 to 8 x 10-7  SIR ISAAC NEWTON He discovered the range of wavelength in the visible light when he refracted white light with a prism. Wavelengths of the Colors of Light Color Wavelength Red 760 nm Orange 610 nm Yellow 590 nm Green 550 nm Blue 470 nm Violet 410 nm USES OF VISIBLE LIGHT USES OF VISIBLE LIGHT USES OF VISIBLE LIGHT MEDICAL USES OF VISIBLE LIGHT LASIK Eye Surgery  INCANDESCENCE It is the emission of light when an object is heated to a high temperature. Examples: Burning wood and electric bulbs.  BIOLUMINESCENCE This is a form of luminescence exhibited by living organisms possessing a light-producing substance called luciferin.  ULTRAVIOLET RADIATION It has frequencies ranging from 8 x 1014 to 4 x 1017 It has wavelengths ranging from 6 x 10-10 to 4 x 10-7 Also known as UV rays. UV stimulates the production of vitamin D in the body It has 3 types: UVA, UVB and UVC JOHANN WILHELM RITTER A German physicist who discovered ultraviolet radiation.  UV-A It has a wavelength ranging from 315 nm to 400 nm. It accounts for 95% of the solar UV reaching Earth. Less intense than UVB. It penetrates the skin deeply to the dermis. It has longer wavelength and is associated with skin aging , tanning and sometimes sunburns. UV-A is used to treat skin conditions such as psoriasis and vitiligo that cause depigmentation of the skin.  UV-B It has a wavelength ranging 280 nm to 314 nm. Most UVB is filtered by the ozone in the atmosphere. It affects the epidermis of the skin. Overexposure causes suntan, sunburn and, in severe cases, blistering. UVB is connected to the Sun Protection Factor (SPF) on labels of sunscreen products.  UV-C It has a wavelength ranging from 60 nm to 279 nm. It is the most damaging type of UV radiation. It is almost absorbed by the atmosphere. It does not reach the Earth’s surface. The only way humans could be exposed to this type of radiation is through artificial source like lamps or laser.  SOURCES OF UV RAYS A major source of UV rays is the sun. Special lamps also emit UV rays. UV light also known as black light. USES OF ULTRAVIOLET RADIATION USES OF ULTRAVIOLET RADIATION USES OF ULTRAVIOLET RADIATION  WILHELM CONRAD ROENTGEN He discovered x-rays. He called it x-rays because he did not know their nature and origin. He was awarded the 1901 Nobel Prize in Physics for his accidental discovery of x-rays.  X-RAYS Sometimes called Roentgen ray. Classified as either soft or hard, x- rays have wavelengths ranging from 10-12 to 10-8 m.  X-RAYS Soft x-rays have lower energy than hard rays. They can penetrate through soft substances such as flesh and bones. Hard x-rays are more penetrating and is mainly used in industries.  SOURCES OF X-RAYS X-rays are produced by the sun and other stars. They are also produced when accelerated electrons hit a metal and some medical equipment. USES OF X-RAYS X-RAY DIFFRACTION OF DNA  GAMMA RAYS Gamma rays has the shortest wavelength and highest frequency of all the electromagnetic waves in the spectrum. Thus, it is highly penetrating. It has a very short wavelength from less than 10-14 to 10-10 m  PAUL VILLARD A French chemist and physicist credited for the discovery of gamma rays in 1900.  USES OF GAMMA RAYS Gamma rays are used in industries to detect crack in metals and to sterilize equipment and commercial products. Food irradiation uses gamma rays to kill bacteria, insects and parasites that can cause foodborne diseases. Gamma radiation is used to eradicate pests.  EXTERNAL INTERNAL RADIOTHERAPY RADIOTHERAPY WHAT DO YOU THINK ARE THE ADVERSE EFFECTS OF TECHNOLOGY WITH ELECTROMAGNETIC RADIATION?  Most of the technology today emit electromagnetic radiation. These radiations can penetrate and affect you compromising your health and disturbing the environment.  Just like their uses, hazards brought by EM waves depend on their frequency. The energy of an electromagnetic radiation is dependent on its frequency. “The higher the frequency, the greater the energy of the radiation.”  Based on its energy EM radiation may be ionizing or non- ionizing. An ionizing radiation has sufficient energy to induce ionization( process of removing one electron from a neutral atom) Exposure to high level ionizing radiation may either cause either an immediate or delayed effect.  An immediate effect can be death or radiation burns. In addition, ionizing radiation can produce molecular changes that can lead to damage in biological tissues, including effects on DNA. Delayed effects can be cancer or mutation, which may affect the person exposed to radiation or their offspring. Ionizing radiations include x-rays and gamma rays. Mutations on animals, humans and plants.  Non-ionizing radiation includes the other parts of the EM spectrum. Although considered less dangerous than the ionizing type, it still poses certain health issues. Both radiowaves and microwaves can interfere with a pacemaker, a medical device that uses electrical impulses to help regulate the beating of the heart. Pacemaker  Microwaves are known to cause cataracts. Overexposure to infrared radiation causes burns or pains. Excessive exposure to visible light , especially in the blue region can cause eye damage. Lasers can cause blindness.  Exposure to sudden burst of intense light, can cause flash blindness that can last for seconds up to a few minutes. Prolonged exposure UV rays burns the skin, and produces the so-called sun tan. UV rays can damage the retina so make sure that your sunglasses provide UV protection.  The greenhouse effect resulting from increased concentration of greenhouse gases as a result of human activity is called anthropogenic greenhouse effect. “The more greenhouse gases there are in the atmosphere, the greater amount of trapped infrared waves and the greater rise in temperature.” It is the anthropogenic greenhouse effect that leads to global warming.  Planktons sinks deeper into the water when exposed to too much UV. This decreases the amount of visible light planktons receives, thereby hindering photosynthesis and growth. Interference from electronics and AM radio signals can disrupt the internal magnetic compasses of migratory birds. Ionizing radiation that comes from nuclear material may result in the weakening of plant seeds and mutations.  The energy (E) of a wave is related to its frequency (f) by the following equation, E= hf E= energy (J) h= Planck’s Constant= 6.63 x 10-34 J.s f = frequency (Hz) Sample Problem The frequency of the red part of visible light is 3.95 x 1014 Hz. How much energy does the color red emit? Given: f= 3.95 x 1014 Hz Required: E=? h = 6.63 x 10-34 Hz Solution: E= hf E= (6.63 x 10-34 J.s )(3.95 x 1014 Hz ) E= 2.6x 1014 J Sample Problem What is the frequency of an electromagnetic wave that has an energy of 1.989 x 10-10 J? Given: E= 1.989 x 10-10 J Required: f = ? h= 6.63 x 10-34 J.s Solution: E= hf f= E / h f= (1.989 x 10-10 J) ÷ (6.63 x 10-34 J.s) f= 3 x 1023 Hz