Radiation Microwave

THE EXISTENCE OF microwaves was first postulated by James Clerk Maxwell in 1864 and confirmed by the experiments of Heinrich Hertz some 20 years later. Microwaves are subdivided into categories as listed in Table 1.

Table 1: Microwave frequency bands as defined by the Radio Association of Great Britain

Designation

Wavelength *

L band

15 cm - 30 cm

S band

8 cm - 15 cm

C band

3.75 cm - 8 cm

X band

2.50 cm - 3.76 cm

Ku band

1.7 cm - 2.50 cm

K band

1.1cm - 1.7 cm

Ka band

0.75 cm - 1.1 cm

Q band

0.6 cm - 1 cm

U band

0.5 cm - 0.75 cm

V band

0.4 cm - 0.6 cm

E band

0.33 cm - 0.5 cm

W band

0.3 cm - 0.4 cm

F band

0.2 cm - 0.33 cm

D band

0.27 cm - 0.18 cm

*Note the definition is originally in units of GHz and has been converted here to cm for comparison to the other measurements. This has inevitably led to some rounding.

*Note the definition is originally in units of GHz and has been converted here to cm for comparison to the other measurements. This has inevitably led to some rounding.

Microwaves are most well known in popular culture for their role in heating food (in a microwave oven), and for their use in mobile telecommunications such as mobile phones and wireless networking. Microwave ovens work by passing S-band radiation though food, which excites water, sugar, and fat molecules. These molecules in turn reradiate in the infrared to heat the food. With the rapid expansion of mobile phone technology, many studies have been done to look at the effects of microwave radiation on human health. The studies show mixed results however, and the general conclusion is that only doses high enough to heat up tissue are likely to have negative impacts.

SEE ALSO: Radiation, Absorption; Radiation, Ultraviolet;

Technology.

BIBLIOGRAPHY. Thormod Henrikson and David H. Maillie, Radiation and Health (Taylor & Francis, 2002); James R. Mahan, Radiation Heat Transfer: A Statistical Approach (Wiley & Sons, 2002) Monika Willert-Porada, Advances in Microwave and Radio Frequency Processing: 8th Inter-

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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