P1.6

P1.6

1. The electromagnetic spectrum: They are electric and magnetic disturbances that can travel through a vacuum. There are 7 different types: Radio, Microwaves, Infrared, Light, UV, X-rays and gamma. The higher the frequency of the wavelength the more energy it carries. Radio waves have the biggest wavelength and gamma the smallest.

   • Wave speed (v) = Frequency in Hertz (f) * Wavelength in metres

2. Visible light is part of the elcromagnetic spectrum, can be used for photography. Infrared radiation is beyond red, given out by all objects, the hotter the object is the more IR radiation it emits. MIcrowaves are used in communication, for the internet and mobile signals, no signs that they are dangerous, yet. Radio and TV waves transport radio and Tv signals.

3. Radio waves of different frequencies are used for different purposes. Microwaves are used for satellites.

   • Optical fibres: Very thin glass fibres that transmit signal by visible light, the rays travel through the fibre by repeated total internal refraction. They carry much more information than radio waves or microwaves.

4. The Doppler effect: When a wave source moves, relative to the observer, this changes the frequency and wavelength of the waves detected

   • Red-shift indicates something moving away. All light from distant galaxies show red shift therefore this shows evidence that the universe is expanding.
   • The universe started with the Big Bang, it should have produced a large amount of gamma radiation. As the universe expanded this would have become lower level radiation; this is the onlyexplanation of CMBR (Cosmic microwave background radiation)

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