Year 11 Physics: the World Communicates Dot Points

The World Communicates 1. The prosper model groundwork be manipulationd to explain how authorized technologies transfer education * describe the aught transformations required in unrivaled of the following mobile telephone, fax/ modem, radio set and television Energy transmission in mobile telephone ound coil energy (input conk pop) -> electrical (in transmitting phone) > radio moving ridge (transmit signalize) -> electrical (in receiving phone) -> sound (output sound) * describe plucks as a transfer of energy disturbance that whitethorn occur in one, two or three dimensions, depending on the nature of the gesture and the culture mean(a) A wave is a travelling disturbance which transfers energy without transporting matter. They may occur in 1D, 2D or 3D, depending on the nature of the wave and the mass medium. D- slinky, laser conflagrate >>> only moves in one direction 2D- peeing wave >>> propagates in each(prenominal)(prenominal) directio ns on a superstar plane 3D-light, sound, all EM waves >>> spreads/ radiates in all directions from a single signalize *identify that mechanized waves require a medium for propagation while electromagnetic waves do not Mechanical waves require a medium (particles in order to propagate) while electromagnetic waves do not. Classification of Waves in terms of medium > mechanical (requires), electromagnetic (doesnt require) -in terms of particle vibration > mechanical >>> transverse (perpendicular), longitudinal ( mate) * define and apply the following terms to the wave model medium, displacement, amplitude, period, compression, r arfaction, crest, trough, transverse waves, longitudinal waves, frequency, wavelength, velocity Mechanical Waves -require a medium to propagate -involves the transfer of energy by a medium by the motion of particles of the medium itself -particles moves as oscillations or vibrations around a fixed pointTransverse waves (e. g. light) mech anical waves particles of the medium oscillate back and forth in a direction perpendicular to the direction of wave propagation -does not require a medium Longitudinal/compressional waves (e. g. sound) -mechanical waves -particles of the medium oscillate back and forth in a direction parallel to the direction of propagation -requires a medium Period (T) magazine taken for a single wave to pass through a fixed point OR the time taken for a particle of a medium to make one complete oscillation (measured in atomic sum 16s) -T = 1fFrequency (f) numerate of waves that pass through a fixed point per second OR number of complete oscillations of a medium particle in one second (measured in hertz > Hz) Medium material through which a wave can propagate Displacement-shortest distance from initial position to final position of a particle Amplitude (A) maximum displacement of particles from the undisturbed state (equilibrium position) Compression zones where particles are closer toge ther than in their undisturbed state Rarefaction zones where the particles are further apart than in their undisturbed state Crest- highest part of the wavesTrough- lowest part of the wave Wavelength (? ) distance between 2 successive identical points on a wave (e. g. distance measured in metres, between adjacent crests or troughs) swiftness (v) speed at which the wave transfers energy away from the source * describe the relationship between particle motion and the direction of energy propagation in transverse and longitudinal waves Particles in a transverse wave oscillate back and forth in direction perpendicular to direction of propagation.Particles in a longitudinal wave oscillate back and forth in direction parallel to direction of propagation. * quantify the relationship between velocity, frequency and wavelength for a wave Velocity is directly proportional to the product of the frequency and wavelength of the wave. 2. Features of a wave model can be used to account for the properties of sound * identify that sound waves are vibrations or oscillations of particles in a medium Sound Waves -are vibrations or oscillations of particles in a medium classed as a mechanical longitudinal wave -when sound wave propagates, vibrations of the particles create pressure variations within that medium -frequency of a sound is determined by the frequency of the accredited vibration,NOT by the medium it travels through (i. e. frequency of a sound doesnt change through any medium) -speed of sound is divergent in different media -sound travels fastest in solids, followed by liquids therefore gases (i. e. high density- particles packed more closely together- vibrations travel faster) -speed of sound in air = 343 m/s relate compressions and rarefactions of sound waves to the crests and troughs of transverse waves used to reconcile them Compressions > crests Rarefactions > troughs * explain qualitatively that pitch is related to frequency and volume to amplitude of sound waves The amplitude of a sound wave determines the volume of the sound. high amplitude = high volumelow amplitude=low volume Likewise, the frequency of a sound wave is directly related to the pitch of a sound. The higher the frequency, the more vibrations per second, and thus, the higher the pitch.High frequency= high pitchlow frequency=low pitch * explain an echo as a reflection of a sound wave Echo forms when a sound wave reflects off a hard surface and rebounds back to its original source, essentially becoming the reflection of a sound wave. wide potpourri of applications including SONAR (Sound Navigation And Ranging) > method for finding the depth of water and detection of animals and other objects in water * describe the principle of superposition and compare the resulting waves to the original waves in sound Superposition- also known as wave interference when two or more waves of the selfsame(prenominal) type pass through the same medium at the same time, they wil l interfere with each other -individual factor waves will interfere to give the resultant wave -position of any point on the resultant wave is the sum of the amplitudes of the component waves -rules to superimpose component waves 1. End points 2. Intersecting points 3. Crests/ Troughs -note > geld + curve = curve gt curve + line = curve > line + line = line > once component waves no longer interfere with each other, they will return to their initial state -constructive interference > component waves are in phase (crests and troughs aligned) -destructive interference > component waves 180? out of phase (crests of one wave aligned to troughs of the other and vice versa) > resultant wave is a straight line 3.Recent technological developments have allowed greater use of the electromagnetic spectrum * describe electromagnetic waves in terms of their speed in lacuna and their lack of requirement of a medium for propagation Electromagnetic Waves travel through berth at the speed of light, 310? m/s. do not require a medium to propagate (i. e. can pass through a vacuum, are all transverse waves) e. g. gamma rays, X-rays, ultraviolet, visible (VIBGYOR), infrared, microwaves, radio waves * identify the lectromagnetic wavebands filtered out by the nimbus, especially UV, X-rays and gamma rays Waves able to penetrate atmosphere and reach surface of the Earth> visible light, radio waves, microwaves -too much moving-picture show to UV radiation can result in cancers and dangerous mutations -too much exposure to X-rays and da Gamma radiation would quickly kill us -Earths atmosphere has the ability to absorb ay unveiling high energy radiation * identify methods for the detection of various wavebands in the electromagnetic spectrum EM Wave Detectors SourceGamma Geiger Muller tube Nuclei of radioactive atoms and cosmic rays X-ray Fluorescent screen X-ray tubes Ultraviolet (UV) video/solar cellsFluorescent chemicals Very hot objectsArcs and sparksMercury c apour lamps Visible Photo/ solar cellsEye Hot objectsLampsLasers Infrared Special photographic filmSkinSemiconductor devices such as LDR and photodiode Warm and hot objects (e. g. ire, people) Radio/ Microwaves Aerials connected to tuned electric circuits in radio and TV sets Microwaves and ovensTV and radio transmitters using electric circuits and aerialsOscillating electrons Note the sun is a producer of all EM waves sending all bandwidths to Earth Photographic film detects all EM waves except for radio/ microwaves * where k = pith of energy of source, d = distance away from source, I= glitz explain that the relationship between the fervency of electromagnetic radiation and distance from a source is an example of the inverse square lawIntensity the energy genuine per square metre per second at a distance away from the source Attenuation decrease in the strength of the signal or light -EM waves decrease in intensity the further they are away from the source to reduce attenu ation in long distance talk, signal needs to be either > sent out as a very large strong signal > signals travelling long distances need to be amplified at repeater or booster displace along their path * outline how the modulation of mplitude or frequency of visible light, microwaves and/or radio waves can be used to transmit information Bandwidth space taken up in terms of frequency Modulation process of adding (encoding) signal information to an EM wave Amplitude Modulation -signal wave encoded onto aircraft carrier wave by adding amplitude of signal wave and carrier waves using principle of superposition -turns into resultant modulated wave -information stored in variations of amplitude -constant frequency, changing amplitudes when received, radio receiver will decode variation in amplitude to obtain original signal, which is then amplified Advantages Disadvantages * requires a much smaller bandwidth of frequencies for transmission * number of transmissions possible in the AM band is larger * depend on changing of amplitude through superposition of waves and therefore e very given to interference Frequency Modulation -signal wave added to carrier waves by changing frequency of carrier wave -information stored in variations of frequency -constant amplitude, changing frequencies low signal corresponds to low frequency and vice versa for high signals Note frequency bands = megahertz (MHz)= _x106 m/s Advantages Disadvantages * since FM waves store information on varying frequencies, less prone to interference -harder to influence frequency of a wave by interference and superposition * each transmission utilises a large bandwidth * different transmitters must be allocated different frequency bands for transmission to avoide interference with each other * limited number of transmitters allowable in given area discuss problems produced by the limited range of the electromagnetic spectrum available for communication purposes -each transmission requires different frequency bands, but available bandwidth for certain types of EM waves is limited so theres a possibility may run out of bandwidth and have transmissions start interfering with each other 4. Many communication technologies use applications of reflection and refraction of electromagnetic waves * describe and apply the law of reflection and explain the effect of reflection from a plane surface on waves reproval When a wave strikes a boundary, it bounces back.This is known as the reflection of a wave. Law of Reflection angle of incidence is equal to the angle of reflection misadventure ray, reflected ray and the normal are on the same plane * describe ways in which applications of reflection of light, radio waves and microwaves have assisted in information transfer Light > fibre optic communcation Radio waves > AM/ FM radio transmission Microwaves > microwave repeating stations (to boost intensity of received signals through use of parabolic concave surface of sate llite dishes) > mobile phone, internet cable data describe one application of reflection for each of the following plane surfaces, concave surfaces, convex surfaces, radio waves being reflected by the ionosphere Plane > dressing and shaving Parabolic concave > satellite dishes (to reflect incoming signals to an antenna at the focus, hence amplifying signal), used in microwave repeating stations and radar control towers to boost intensity of received signals) >produce parallel beams of light used in torches, car headlight, etc Convex > shop security mirrors and side view mirrors (provides wider range of view) Radio waves reflected by ionosphereIonosphere region of Earths atmosphere which consists of charged particles (electrons and ions) -charged property allows it to reflect low frequency (high wavelength) EM waves such as radio waves -this reflection property enables the transmission of radio waves to receivers that are out of sight due to the Earths curvature * explain that refraction is related to the velocities of a wave in different media and outline how this may result in the bending of a wavefront Wavefront a line that joins all the point that are in phase in a wave (e. . a line that joins all crests, so is perpendicular to direction of propagation) Refraction when waves travel from one medium to another, where they experience a change in speed, travel different distances (for the same interval of time), causing its wavefronts to bend. This changes the direction of propagation of the wave. Exception when wave hits boundary between the two media at right angles, incident wavefronts are parallel to boundary, or incident angle is 0? -wavelength and velocity change -frequency remains the sameWhen a wave travels from a more dumb to a less dense medium, direction of wave bends away from the normal and vice versa. Note deep water is less dense than shallow water * define refractive index in terms of changes in the velocity of a wave in passing from one medium to another refractile Index the absolute refractive index of a material is a ratio of the speed of light in a vacuum to the speed of light in the material RI = cv , where c is the speed of light, and v is the speed of light in material It is the change in velocity of a wave passing from one medium to another. related to optical density (i. e. high RI = high OD and vice versa) * define Snells Law = = n? n? * identify the conditions necessary for total internal reflection with reference to the tiny angle Total internal reflection occurs when the incidence angle is greater than the critical angle. * i. e. boundary alone reflects the waves, hence the wave never escapes the medium it is in Critical angle wave travelling from more dense to less dense angle of incidence forms an angle of reflection of 90? the critical angle) * outline how total internal reflection is used in optical fibres Fibre-Optic converse optic fibres made of glass or plastic materials -An opti cal fibre consists of a core (made of material with higher RI/ is more optically dense) and a cladding Light encoded with data is guided along the length of the fibre via total internal reflection until it reaches the other end where the information is extracted and decoded Advantages How/ Why large amount of data can be transmitted at any one time * suitable for transmitting information where straight line transmission is unacceptable * interferences by outside disturbances are minimised since light waves are confined within fibres * energy lost due to long distance transmission minimised * by using a group of many fibres * light waves only travel in straight lines * light waves are confined within fibres * energy of light waves totally trapped within core of fibres . Electromagnetic waves have potential for future communication technologies and data storage technologies * identify types of communication data that are stored or transmitted in digital form * fibre optic communica tion * AM/FM radio broadcasting * mobile telephone calls * satellite communication