Radio waves, microwaves, infra red and visible light can be used for communication.
Radio waves are used to transmit __________ and __________ programmes between different points on the Earth’s surface. Longer wavelength radio waves are __________ from an electrically charged layer in the Earth’s upper atmosphere, called the __________.
This enables 'information' to be sent between distant points despite the curvature of the Earth’s surface.
Microwaves can pass through the Earth’s atmosphere and are used to send information to and from __________ and within mobile phone networks. Microwave radiation has wavelengths that are strongly absorbed by water molecules and can also be used for __________.
Infra-red (same as we discussed for heat ) is used for short range communication through air. It is used for remote controls and IrDA ports on mobile phones, computers and printers.
Infra red and visible light can be used to send signals along optical fibres and so travel in curved paths. Because infra red and visible light has a __________ frequency, information can be sent __________.
The light under goes 'Total Internal Reflection' and so travels along the fibre even around corners.
Light is totally relected by the internal surface of the glass fibre.
For more information see
Health Concerns
There is a health concern about the amount of energy absorbed by the brain when using mobile phones. Advice from the Stewart Report said that adults should limit the amounts of time spent on the phone, and for children the advice was much stronger. The Stewart Report recommends that under-16s use their phones only for essential calls. This is because children's skulls are thinner than adults and so their skull absorb less of the microwaves, leaving their brain less protected.
You phone will have a Specific Absorption Rates (SAR) rating. It is a reliable measure of its ability to cause cell damage and is a way of measuring the quantity of radiofrequency (RF) energy that is absorbed by the body. The LOWER the better. Look up yours on the manufactures websites: Motorola; Nokia; Samsung; Sony Ericsson.