Light Waves and Electromagnetic Waves

(A) Wave nature of light

Light is a wave. It shows all properties of waves including interference and diffraction.

(B) Light and the electromagnetic spectrum

The visible light is part of the electromagnetic spectrum, which includes radio waves, microwaves, infra-red radiation, visible light, ultraviolet radiation, X-rays and gamma rays (in an ascending order of frequency). The wavelength of visible light ranges from about 400 nm (violet) to 700 nm (red) in a vacuum.EM waves have a lot of applications in daily life.

Characteristics of EM waves:

EM waves are transverse waves.

EM waves travel at a fixed speed of 3 x 108 m s-1in a vacuum.

EM waves obey v = fλ.

EM waves show reflection, refraction, diffraction and interference.

EM waves can travel in a vacuum.

Source / Detector / Use / Danger
radio waves / radio transmitter
lightning
stars / radio telescope
radio
antenna / radio and TVbroadcast
telecommunication (e.g. aircraft
and taxi)
mobile phone communication
study of the universe / posing potential risk to the health
Microwaves / microwaves transmitter
stars / microwave telescope
microwavereceiver / cooking (microwave oven)
traffic speed camera
radar (navigation, weather forecast)
satellite telecommunication
study of the universe / cataracts (clouding of lens in eyes)
Infra-red radiations / lamp
flame
hot objects
stars(e.g. sun) / skin
IR film
IR telescope / remote control
heat lamp (for healing sport injuries)
satellite IR imaging
measuringtemperature (thermometer)
thermographs
night vision system
auto-focusing (camera)
burglar alarm system
data transmission
study of the universe / over-heat
Visible light / lamp
flame
very hotobjects
stars (e.g. Sun) / eyes
photographic film / vision
photocell
laser (e.g. pointer, CD player, printer)
satellite imaging
study of the universe / damage to the retina
Ultraviolet radiations / white hot objects
mercury lamp
UV lamp
stars (e.g. Sun) / ultraviolet telescope
fluorescent material
photographic film / detection of fake banknotes
sterilization (drinking water and medical equipment)
sun-tan
production of vitamin D in human body
study of the universe sunburn / skin cancer
X-rays / X-ray tube
stars / X-ray detector
photographic film / medical imaging
airport security checks (luggage)
study of the universe / cell damage
cancer
Gamma Rays / radioactive substance on Earth
cosmic rays
stars / G-M counter
photographic film / radiotherapy (kill cancer cells)
sterilization (food and medical equipment)
medical imaging
study of the universe / Cell damage
DNA mutation
cancer

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Light Waves and Electromagnetic Waves