Wave Theory

Wave:

. Disturbance which transfers energy through medium.
. Medium is substance/material that carries wave through it.
  Ex: Air, Water
. It involves periodic, repetitive movement.

Types of Waves:

 a. Depending on orientation of particles:

    1. Longitudinal Waves: Movement of particles are parallel to motion of energy.
                                          Ex: Sound
    2. Transverse Waves: Movement of particles are perpendicular to motion of energy.
                                          Ex: Movement of wave in stretched rope.
    3. Surface Waves:  Particles travel in circular motion.
                                          Ex: Ripples in bucket of water.

 b. Depending on type of matter they are able to travel:

    1. Electromagnetic waves: Doesn't require medium, can travel through vacuum.
                                               Ex: Light
    2. Physical Waves: Require medium to travel.
         > Longitudinal Waves: Liquids, gases.
         > Transverse Waves: Solids.

Features of Wave:

 Crest: Highest point in wave.
 Trough: Lowest point in wave.
 Amplitude: Amount of displacement from equilibrium.
 Period: Time it takes for successive crests or troughs to pass specific point.

Frequency: 
  . Number of waves that pass a point per unit time.
  . It is inverse of time.
  . Units are Hertz (Hz).
  Ex: Wheel completing 25 revolutions in 1 second, Frequency= 25 hz.

Wavelength:
  . Distance between consecutive corresponding points of same phase like crests, troughs.
  . Designated by Greek letter λ.

Relation between Frequency and Wavelength:
  . Electromagnetic waves travel at same speed i.e. c=299,272 km per second. Approximately 3*10^8 m per second.
  . In Electromagnetic spectrum, there are different types of waves with varying frequency and wavelength.
    

  

Electromagnetic Spectrum:

 . Describes range of energy associated with different forms of radiation.
 . Travels in spaces as packets energy called photons.
 . Energy associated with photons determines position in Electromagnetic spectrum.
 . All the waves in spectrum travels with same speed 299,272 km per second.
 . Frequency, wavelength, energy varies.
 


NameFrequencyWavelengthEnergyUses
Radio Waves3Hz-300GHz1mm-km12.4feV-1.24meVBroadcast radio, television
Micro Waves300MHz-300GHz1mm-1meter1.24ueV-1.24meVCooking, radar & others
InfraredWaves300GHz-405THz750nm-1mm12.4meV-1.7eVTransmit heat from sun, fires, TV remote controls
Visible405THz-790THz390nm-750nm1.7eV-33eVMakes things able to be seen
Ultravoilet Waves790THz-30PHz10nm-400nm3eV-124eVAbsorbed by skin, Used in floroscent lamps
X-Rays30PHz-30EHz0.01-10nm120eV-120keVTo view inside of bodies, objects
Gamma rays>10EHz<0.01nm100keV-300+GeVMedicine for killing cancer, sterilizing food.

Audible Frequency Range:

 . A range of periodic vibration whose frequency is audible to average human.
 . It is about 20 Hz- 20 KHz.
 . Frequencies below 20 Hz is generally felt rather than heard.
 . Frequencies above 20 KHz is sometimes sensed by young people , but causes hearing loss.
 . Infrasound: Frequency below human range.
                       Detected by Elephants, Whales.
 . Ultrasound: Frequency above human range.
                       Detected by Bats, Whales, Porpoises, Dolphins.

2G, 3G, 4G Spectrum:

 . Most mobile networks use portions of Radio Frequency spectrum for communication.
 . 'G' stands for generation of wireless phone technology.
 . Improvements are added for every next generation.
 . The differences in various generations:
Parameter2G3G4G
Introduced in199320012009
TechnologyIS 95, GSM3G, WCDMALTE, WiMAX
Access SystemTDMA, CDMACDMACDMA
Speed64 Kbps2 Mbps100 Mbps
Frequency900 MHz2100 MHz800MHz, 1800 MHz
SupportsVoice and DataVoice and DataVoice and Data
Internet ServiceNarrowbandBroadbandUltra Broadband
AdvantagesMultimedia features (SMS, MMS), Internet accessHigh Security, International roamingSpeed, Global mobility
DisadvantagesLow network range, Slow data ratesHigh power consumption, low network rangeHard to implement, complicated hardware implemented
ApplicationsVoice calls, Short messages, partial browsingVideo conferencing, mobile TV, GPSHigh speed Applications, mobile TV, Wearable devices