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P1b revision

Electromagnetic waves
Electromagnetic waves are electric or magnetic disturbances that transfer energy from one place to
another
The amount of energy transferred depends on the wave length
The wave length is the distance from one wave peak to the next wave peak along the waves
The frequency is…

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Remote control handsets
Microwaves
o Shorter in wavelength that radio waves
o Lies between radio waves and infrared radiation
o Used for
Communications ­ can pass through the atmosphere ­ don't spread out as much as radio
waves
Heating food in microwaves ­ unlike infrared, microwaves penetrate food
Radio Waves…

Page 3

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o Can carry much more
information
o More secure
Analogue and digital signals
o Digital Signals ­ sequence
of impulses ­ voltage level
is either high (1) or low (0)
­ mobile phone and
computer signals are digital
o Analogue signal ­ a wave
that varies in amplitude or
frequency…

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Alpha radiation (helium nucleus) is stopped by paper
Beta radiation (fastmoving electron) when through the paper
Gamma Radiation is more penetrating than beta
Most atoms have a stable nucleus that doesn't change
o Radioactive atoms have a nucleus that is unstable that emits alpha, beta or gamma radiation
o Unstable…

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o Radioactive dating
Carbon dating
Used to find the age of ancient wood
Living wood has a tiny proportion of radioactive carbon ­ half life of 5600 years
Uranium dating
Used to find the age of igneous rocks
The rocks contain radioactive uranium ­ half life for 4500 million years…

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