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
Ex: Sound
2. Transverse Waves: Movement of particles are perpendicular to motion of energy.
Ex: Movement of wave in stretched rope.
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.
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.
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.
| Name | Frequency | Wavelength | Energy | Uses |
|---|---|---|---|---|
| Radio Waves | 3Hz-300GHz | 1mm-km | 12.4feV-1.24meV | Broadcast radio, television |
| Micro Waves | 300MHz-300GHz | 1mm-1meter | 1.24ueV-1.24meV | Cooking, radar & others |
| InfraredWaves | 300GHz-405THz | 750nm-1mm | 12.4meV-1.7eV | Transmit heat from sun, fires, TV remote controls |
| Visible | 405THz-790THz | 390nm-750nm | 1.7eV-33eV | Makes things able to be seen |
| Ultravoilet Waves | 790THz-30PHz | 10nm-400nm | 3eV-124eV | Absorbed by skin, Used in floroscent lamps |
| X-Rays | 30PHz-30EHz | 0.01-10nm | 120eV-120keV | To view inside of bodies, objects |
| Gamma rays | >10EHz | <0.01nm | 100keV-300+GeV | Medicine 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:
| Parameter | 2G | 3G | 4G |
|---|---|---|---|
| Introduced in | 1993 | 2001 | 2009 |
| Technology | IS 95, GSM | 3G, WCDMA | LTE, WiMAX |
| Access System | TDMA, CDMA | CDMA | CDMA |
| Speed | 64 Kbps | 2 Mbps | 100 Mbps |
| Frequency | 900 MHz | 2100 MHz | 800MHz, 1800 MHz |
| Supports | Voice and Data | Voice and Data | Voice and Data |
| Internet Service | Narrowband | Broadband | Ultra Broadband |
| Advantages | Multimedia features (SMS, MMS), Internet access | High Security, International roaming | Speed, Global mobility |
| Disadvantages | Low network range, Slow data rates | High power consumption, low network range | Hard to implement, complicated hardware implemented |
| Applications | Voice calls, Short messages, partial browsing | Video conferencing, mobile TV, GPS | High speed Applications, mobile TV, Wearable devices |