ELECTROMAGNETIC WAVES
ELECTROMAGNETIC WAVES
Electromagnetic wave: is self-propagating transverse oscillating wave of electric and magnetic fields.
Electromagnetic radiation (Em radiation or Emr) is a form of energy emitted and absorbed by charged particles, which exhibits wave - like behavior as it travels through space. EMR has both electric and magnetic field components which stand in a fixed ratio of intensity to each other, and which oscillate in phase perpendicular to each other and perpendicular to the direction of energy and wave propagation.
EMR is classified according to the frequency of its wave. The electromagnetic spectrum, in order of decreasing wavelength and increasing frequency, we have
→ Radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.
SOURCES OF ELECTROMAGNETIC WAVES
Type
|
Source
|
Typical wavelength
|
Gamma ray
|
Emitted by Radioactive sources
|
10 -14
|
X – ray
|
Produced by X –ray tube, fast electrons stopped by a target
|
10-10
|
U –v
|
From sunlight and quartz lamps, electric discharge, through gases
|
10-8
|
Visible light
|
From sunlight, lamps
|
10-7
|
Infrared
|
Heat radiation emitted by hot objects
|
10-5
|
Radio wave
|
Emitted by radio antenna
|
10-1 to km
|
PROPERTIES OF ELECTROMAGNETIC WAVES
1. They contain momentum and angular momentum
2. It consists both electric and magnetic field
3. It travels in a vacuum
4. It moves with the speed of light i.e. 3.0 x 108m/s
5. It is transverse
6. It exhibit the characteristic of:
- Diffraction, polarization, interference, reflection, refraction
EFFECT OF ELECTROMAGNETIC WAVES
The effect of EMR (Electromagnetic radiation) upon biological systems (and also to many other chemical systems, under standard conditions) depends both upon the radiation’s power and frequency. For lower frequencies of EMR up to those of visible light (i.e. radio, microwave, infrared), the damage done to cells and also to many ordinary materials under such conditions is determined mainly by heating effects, and thus by the radiation power. By contrast, for higher frequency radiations at ultraviolet frequencies and above (i.e. X-rays and gamma rays) the damage to chemical materials and living cells by EMR is far larger than that done by simple heating, due to the ability of single photons in such high frequency. EMR to damage individual molecules chemically i.e.
Ultraviolet rays
- Causes lasting damage to DNA (Molecular damage), Cause cancer,
Skin burns (sunburn) → this is due to quantum effects, which causes permanent damage to materials and tissues at the single molecular level.
Infrared is reflected by metals into ultraviolet but is absorbed by a wide range of substances, causing them to increase in temperature as the vibration dissipates as heat.
APPLICATION OF ELECTROMAGNETIC WAVES
1. Useful in telecommunication: GPRS, Rader for satellite, GSM, etc.
2. Useful for medical purposes: Radiography, Radiotherapy, treatment of abnormal growth
3. For detection of cracks in metals To study the behavior of crystal - crystallography
4. For detection of contraband at the airport
5. Useful in the use of electronic gadget e.g. T.V, A/C, cars, automatic doors etc.
6. To study the behavior of crystal-crystallography
MATHEMATICAL REPRESENTATION:
Velocity/speed of wave=frequency x wavelength
Velocity is measured in m/s, frequency measured in hertz (Hz),
Wavelength measured in meters (m)
SAFETY USE OF ELECTROMAGNETIC WAVE:
I.Wear gloves in handling EMR devices 2.wear dosimeters
3.wear goggle in handling welding machine 4.keep EMR substances in safe glassware
KEY WORDS:
Electromagnetic spectrum–The continuous series of electromagnetic waves in order of wavelength or frequency.
Frequency –The number of waves passing a point every second, measured in hertz (Hz).
Gamma rays– Electromagneticwaves with the shortest wavelengths. Uses include sterilizing medical equipment and cancer treatment.
Infrared waves–Electromagnetic waves given off by hot objects. Uses include heating, cooking and remote controls.
Microwaves–Electromagnetic waves that are short-wavelength radio waves. Uses include mobile phones, radar and cooking.
Radio waves– Electromagnetic waves with the longest wavelengths. Used for communications.
Ultraviolet rays– Electromagnetic waves that can be absorbed by certain chemicals and emitted as visible light. Uses include tanning beds and security marking.
Wavelength –The distance between two matching points on neighbouring waves, which is measured in metres.
Visible light–Electromagnetic waves that are detected by our eyes, allowing us to see. Other uses include optical fibre communications and imaging.
X-rays–Electromagnetic waves that pass through most materials. Uses include medical imaging and security.
Comments
Post a Comment