Introduction
- Wavelength of the ElectroMagnetic spectrum continually changes
- high frequency = short wavelength
- high frequency = high energy
- high energy = more dangerous
The video and text below describe some of the qualities and uses of different waves on the electromagnetic spectrum.
Radio Waves (communications)
- TV and FM radio (short wavelength)
- Direct line of sight with transmitter (do not diffract)
- Medium wavelength – travel further because they reflect from layers in the atmosphere
Satellite signals (Microwaves)
- Frequency of microwaves pass easily through atmosphere and clouds
Cooking (Microwaves)
- Microwaves are absorbed by water molecules.
- These water molecules become heated > heat food
- Dangers: microwaves are absorbed by living tissue Internal heating will damage or kill cells
Infrared Radiation (remote controls, toasters)
- Any object that radiates heat radiates Infrared Radiation
- Infrared Radiation is absorbed by all materials and causes heating
- It is used for night vision and security cameras as Infrared Radiation is visible in daytime or night-time
- Police use it to catch criminals, army use it to detect enemy
- Dangers: damage to cells (burns)
Ultraviolet
- Dangers:
- over-exposure to UVA and B damages surface cells and eyes and can cause cancer.
- There is a problem with current sunscreens which protect against skin burning from high UVB but give inadequate protection against free radical damage caused by UVA.
- Dark skins are not necessarily safer from harm.
- Sun exposure for the skin is best restricted to before 11am and after 3pm in the UK in summer months.
- over-exposure to UVA and B damages surface cells and eyes and can cause cancer.
- Benefits:
- sanitary and therapeutic properties have a marked effect on architecture, engineering and public health and have done so throughout history.
- UVC is germicidal, destroying bacteria, viruses and moulds in the air, in water and on surfaces.
- UV synthesises vitamin D in skin, controls the endocrine system and is a painkiller.
- Used in state of the art air-handling units, personal air purifiers and swimming pool technology.
- Used to detect forged bank notes: they fluoresce in UV light; real bank notes don’t. Used to identify items outside visible spectrum areas, known as 'black lighting'.
X-rays
- X-rays detect bone breaks
- X-rays pass through flesh but not dense material like bones
- Dangers: X-rays damage cells and cause cancers. Radiographer precautions include wearing lead aprons and standing behind a lead screen to minimise exposure
Gamma Rays
- Gamma Rays cause and treat cancers
- In high doses, gamma can kill normal cells and cause cancers
- Gamma can be used to kill mutated cells though too.
