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Slide 1

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Physics Revision…read more

Slide 2

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P1.1 Energy transfer by heating…read more

Slide 3

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Infrared radiation
· Infrared wave part of electromagnetic spectrum ­ just beyond visible
light
· Detect infrared radiation with our skin ­ makes us feel warm
· All objects emit (give off) infrared radiation
· Hotter an object ­ more IR its emits in a given period time
· IR travel through vacuum, as in travelling through space. This is how
we get energy from the Sun
· Vacuum - A space entirely devoid of matter
Detecting infrared radiation…read more

Slide 4

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Surfaces and radiation
· Dark, matt surfaces are good absorbers of
infrared radiation. An object painted dull black and
left in the Sun will become hotter than the same
object painted shiny white
· Dark, matt surfaces are also good emitters of
infrared radiation ­ so object that is painted dull
black will transfer energy and cool down more
quickly than the same object painted shiny white
· Light, shiny surfaces are good reflectors of IR…read more

Slide 5

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States of matter
· 3 states of matter ­ solids, liquids and gases ­ make substances
change between states by cooling or heating it
· In a solid ­ particles vibrate about fixed positions so solid has a fixed
shape
· In a liquid ­ particles in contact with each other but can move about
at random ­ liquid
· In gas ­ particles are usually far apart and move at random such
faster, so a gas doesn't have a fixed shape and can flow
· Density of a gas is much less than that of a solid and a liquid…read more

Slide 6

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Conduction
· Conduction occurs mainly in solids. Most liquids and all
gases are poor conductors
· If one end of a solid is heated, particles at that end
gain kinetic energy and vibrate more ­ energy is
passed to neighbouring particles and in this way the
energy is transferred through the solid
· Process occurs in metals
· When metals heated their free electrons gain kinetic
energy and move through the metal, transferring
energy by colliding with other particles ­ hence metals
= good conductor
· poor conductors = insulators ­ e.g. wool and fibreglass
are good insulators because they trap air…read more

Slide 7

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