The Nature of Light The Electro The Dual Magnetic Nature of Light Spectrum Luminous and Opaque, Different Illuminated TransparentSources of Light Objects and Translucent
The Dual Nature of LightLight Lightas a as awave particle
The WAVE Theory ofLight The theory that lights is transmitted via wave form was proposed by Christian Huygens in 1679. According to•light corpuscles have mass and travel at extremely the theory:high speeds in straight lines•rectilinear propagation - blocked by large objects(well-defined shadows)•obey the law of reflection when bounced off asurface•speed up when they enter denser media
The Particle Theoryof Light transmitted via corpuscar The theory that light is form was supported and •wavelet envelop model (each point onIsaac Newton. advocated by Sir a wavefront According to his theory: acts as a source for the next wavefront) •plane waves generate plane waves, circular waves generate circular waves •light was composed of longitudinal waves like sound •obey the law of reflection when bounced off a surface
TheElectromagneticSpectrum The electromagnetic spectrum is the range of all possiblefrequencies of electromagnetic radiation. Electromagneticwaves are formed when an electric field couples with amagnetic field. It is a continuum of all electromagnetic wavesarranged according to frequency, wavelength and energy.
frequency, wavelength and energy • Wavelength is inversely proportional to the wave frequency• Photon energy is directly proportional to the wave frequency λ=E/f
Radio waves Microwaves•Have the longest •Very easily absorbed by waterwavelengths but leastenergetic •Cause water and fat molecules to vibrate, which makes the substances hot.•Utilized by antennas •Good for transmitting information•They are used for because microwave energy cantransmission of data, via penetrate haze, light rain andmodulation. snow, clouds, and smoke.•Television, mobile phones, •Mobile phones, fixed traffic speedwireless networking, and cameras, and radar, which is usedamateur radio all use radio by aircraft, ships and weatherwaves. forcasters, all use microwaves.
Infrared Light Radiation Visible light waves are the only•Can be detected by special electromagnetic waves we caninfra-red film. see. We see these waves as the•Primary source of infrared colors of the rainbow.radiation is heat or thermalradiation•Our skin emits infrared light,which is why we can be seen inthe dark by someone usingnight vision goggles.•Ex. remote control
UV rays X-rays•Main natural source is the sun •Also called as Roentgen raysand other stars in honor of their discoverer•Can break chemical bonds, •Given off by stars and aremaking molecules unusually strongly emitted by somereactive types of nebulae.•Often harmful to plants and •Have so much energy andanimals, including humans such a short wavelength that they can go right through you•Used to kill microbes, getting • Used by doctors to seea sun tan, detecting forged inside peoplebank notes
Gamma Rays•Shortest-wavelength, Highest energy•Most dangerous and most penetrating ofall electromagnetic radiation, and arequite difficult to stop•Result of violent cosmic events such assupernovas, other nuclear explosions, andradioactive decay•Used to kill cancer cells ("Radiotherapy")
Light SourcesLight is a form of energy. To create light, another form of energy must be supplied. There are two common ways for this to occur, incandescence and luminescence.
"Black body radiation" It is the emission of light from a hot body as a result of its temperature.Incandescence Involves the vibration of entire atoms Sunlight, regular light bulbs (not florescent) and fires are all incandescent sources of light. "Cold light" It is the emission of light by a substance not resulting from heat. It can be caused by chemical reactions, electrical energy, subatomic motions, or stress on a crystal. Luminescence Involves only the vibration of electrons Ex. computer monitors, televisions, and florescent lights, fireflies
Luminous and Illuminated BodiesThe objects that we see can be placed into one of two categories:luminous objects and illuminated objects. Luminous objects areobjects that generate their own light. Illuminated objects areobjects that are capable of reflecting light to our eyes.
A luminous body, such as the sun, another star,or a light bulb, is thus distinguished from anilluminated body, such as the moon and mostof the other objects one sees. Luminous objectsgive off light whereas illuminated objectsrelfect light. Examples of luminous bodies arethe sun, stars, fireflies, lighted candle, light Illuminated bodies not onlybulbs.. reflect light but sometimes also transmit it, such as the opaque, transparent and translucent
Translucent TransparentObjects Objects•These kinds of objects scatter ordisperse light when light falls on •They are those that allowthem. light to pass through readily.•They are said to transmit light in •These kind of objects havethe absence of details absolute clarity.•You can only see a blur image •You can see right throughwhen you peek through these them.•Frosted glass and waxed paper •The water, air and glass areare examples of translucent all transparent objects.objects.
Opaque Objects•These objects do not allow light to pass through.•They absorb some of the light that is cast onthem.•Wood, paper and many more are examples ofsuch objects.