Physics P1

 All objects emit and absorb infrared radiation.

The hotter an object is the more infrared radiation it radiates in a given time.

Dark, matt surfaces are good absorbers and good emitters of infrared radiation.

Light, shiny surfaces are poor absorbers and poor emitters of infrared radiation but are good reflectors of infrared radiation.

Energy can be transferred usefully or stored but cannot be created or destroyed.

When energy is transferred only part of it may be usefully transferred, the rest is ‘wasted’.

Wasted energy is eventually transferred to the surroundings, which become warmer. The wasted energy becomes increasingly spread out and so becomes less useful.

Underground :

* aesthetically preferable as can't be seen

* fewer problems with vegetation, lightening, vandalism and car accidents

* requires smaller right-of-way and disturbs less space

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* a lot more expensive than overhead cables to construct

* a lot more expensive to repair

* can be a risk with careless digging

Overhead:

* cheaper than underground to contruct and repair

* can be used in the country when there are farm houses isolated/far away from each other and underground cables aren't suitable

* suspected health risks of surrounding areas

* ruins landscapes/views and vegetation

* more vulnerable to vandalism, lightening and can cause car accidents

Step UP transformer: Increases the voltage to go along the power cables to increase efficiency and decrease loss of energy through heat

*Has more coils on the secondary side 

Step DOWN transformer: Decreases the voltage to go to homes and businesses for safety

*Has more coils on primary side 

In a transverse wave the oscillations are perpendicular to the direction of energy transfer.

In a longitudinal wave the oscillations are parallel to the direction of energy transfer.

Electromagnetic waves are transverse.  Sound waves are longitudinal

All types of electromagnetic waves travel at the same speed through a vacuum (space). Waves undergo a change of direction when they are refracted at an interface

frequency = how many waves

wavelength = length of wave

amplitude = height of wave

■ radio waves – television, and radio (including diffraction effects)

■ microwaves – mobile phones and satellite television

■ infrared – remote controls

■ visible light – photography

Doppler Effect:

■ the wave source could be light, sound or microwaves

■ when the source moves away from the observer, the observed wavelength increases and the frequency decreases

■ when the source moves towards the observer, the observed wavelength decreases and the frequency increases

There is an observed increase in the wavelength of light from most distant galaxies. The further away the galaxies are, the faster they are moving, and the bigger the observed increase in wavelength. This effect is called red-shift. It is evidence for the Big Bang Theory (universe began at a small initial point)

Cosmic microwave background radiation (CMBR) is a form of electromagnetic radiation filling the universe. It comes from radiation that was present shortly after the beginning of the universe.