Light waves

Light waves

1. The Critical angel is the angel of incidence beyond which light will totally internally reflect

2. Large wavelengths refract less and diffract more, while Short wavelengths refract more and diffract less

3. Electromagnetic spectrum

   • can travel through vacuum at speed of 3 X 10^8
   • as the wavelength decrease from left to right, the frequency increase
   • they are electric and magnetic disturbances that transfer energy from one place into another
   • Radio waves --> radio and television communications
   • Microwaves --> satellite television, telephone and microwaves ovens
   • Infra-red --> household electric appliances, television controllers and intruder alarms
   • Visible light --> optical fibers in medical uses and telephones
     • can carry more information that do not weakens as much over long distances
   • Ultra-violet --> fluorescent tubes and sterillisation
   • X-rays --> hospital use in medical imaging and killing cancerous cells engineering application such as detecting cracks in metals
   • Gamma rays --> medical treatment in killing cancerous cells and engineering application such as detecting cracks in metals

4. Modulation and Broadcasting

   • a wave that have been modified to carry a signal to transmit radio waves
   • Amplitude modulation, the rdaio waves varies in amplitude to match the changes in the sound waves of the carrier waves
     • greater area covered by one transmitter which uses smaller bandwidth means more stations available in any frequency range and cheaper radio set
   • FRequency modulation, the radio wave varies in frequency to match the changes if the sound wave of the carrier wave
     • Less electric interference and noise with greater bandwidth which produces a better quality of sound
   • Analogue signals is when data varies continuously with time using electrical impulses to emulate the waveform
     • Uses less bandwidth. More accurate to the original sound
     • Suffer from degradation caused by noise and interference. Produce poor quality sound and vision. The effect of random noise can make signal loss and distortion impossible to recover
   • Digital signals consist of a series of ones and zeros with no intermediate values
     • Much more tolerant to degradation as they maintain their quality over long distance as they can be regenerated eliminating noise. Carry large amount of data per second. More secure because data can be encrypted.
     • Sampling error. Digital communications require greater bandwidth
   • Noise and interference
     • all signals become weaker as they travel long distances and might pick up random extra noise signals as hiss and crackles
     • In Analogue, it add extra information which is amplified each time the signal is amplified which make it impossible to makeout the original sound signal
     • In Digital, the noise is usually lower in amplitude than the ON amplitude so the electronic amplifiers can ignore them so the quality is maintained