GCSE Science A Physics 1 Waves Learning Outcomes 1)Apply the equations; Wave speed = Wavelength × Frequency Speed = Distance Time 2) Compare the use of microwaves and infra-red radiation in long distance communication, 3) Be aware of public concern about claimed health risks associated with mobile phone masts. 1)Apply the equations; Wave speed = Wavelength × Frequency Speed = Distance Time 2) Compare the use of microwaves and infra-red radiation in long distance communication, 3) Be aware of public concern about claimed health risks associated with mobile phone masts.

GCSE Science A Physics 1 Waves Waves and communication Satellite Communications Geostationary orbit: Satellite orbits above the same point on the Earth at all times The satellite takes 24 hours to orbit the Earth. Satellites (mainly) use microwaves to communicate with base stations on Earth. Fibre Optic Cable Use infrared to send information down special cable using “total internal reflection” Speed of infrared radiation in the cable is 2x10 8 m/s Satellite Communications Geostationary orbit: Satellite orbits above the same point on the Earth at all times The satellite takes 24 hours to orbit the Earth. Satellites (mainly) use microwaves to communicate with base stations on Earth. Fibre Optic Cable Use infrared to send information down special cable using “total internal reflection” Speed of infrared radiation in the cable is 2x10 8 m/s

GCSE Science A Physics 1 Waves Waves and communication Satellite CommunicationInfrared Cable Time DelayA couple of secondsFraction of a second BandwidthNot much info can be sent - narrowband Lots of information can be sent – broadband Other infoIf something breaks very difficult to fix. Requires a lot of infrastructure so can be time consuming and costly to implement

GCSE Science A Physics 1 Waves Why is there a time delay when using a satellite? The speed of a wave depends on its frequency and wavelength: Speed = Frequency x Wavelength For all EM waves the result of the equation above is 300,000,000m/s e.g. The frequency of microwaves used for satellite communication is 6Ghz, and the wavelength is 5cm. The speed of a wave depends on its frequency and wavelength: Speed = Frequency x Wavelength For all EM waves the result of the equation above is 300,000,000m/s e.g. The frequency of microwaves used for satellite communication is 6Ghz, and the wavelength is 5cm. But Gamma rays have a higher frequency than microwaves, so how can they travel at the same speed?

GCSE Science A Physics 1 Waves Why is there a time delay when using a satellite? Communication satellites are always about 36,000,000m above the Earth’s equator. Using the equation speed = distance/time, What would be the expected time delay? Communication satellites are always about 36,000,000m above the Earth’s equator. Using the equation speed = distance/time, What would be the expected time delay?

GCSE Science A Physics 1 Waves Why is there a time delay when using a satellite? The typical delay is roughly ms (about a quarter of a second). In reality delays can be much longer, can you think of why?

GCSE Science A Physics 1 Waves Some companies have spent BIG BUCKS, fitting fibre optic cable under the Atlantic ocean. They do this because using this method they can get a signal from New York to London with a delay as low as 60ms! Assuming that there are no routers/switches along the way, how long must this cable be? (remember: the speed of light is slower in a fibre optic cable: 2x10 8 m/s) Some companies have spent BIG BUCKS, fitting fibre optic cable under the Atlantic ocean. They do this because using this method they can get a signal from New York to London with a delay as low as 60ms! Assuming that there are no routers/switches along the way, how long must this cable be? (remember: the speed of light is slower in a fibre optic cable: 2x10 8 m/s)

GCSE Science A Physics 1 Waves Can mobile phones cause brain tumours? Read the articles about mobile phone use. What do you think? Read the articles about mobile phone use. What do you think?

GCSE Science A Physics 1 Waves “The electromagnetic spectrum is like notes played on a piano” In pairs discuss this statement. Then write a short piece discussing the idea. The best one (from the three classes) will win a prize! “The electromagnetic spectrum is like notes played on a piano” In pairs discuss this statement. Then write a short piece discussing the idea. The best one (from the three classes) will win a prize!