# P1

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• P1abcd
• P1a) Heating Houses
• Energy always flows from a warmer body to a colder body
• A thermogram uses colour to show temperature
• When the temperature of a body increases, so does the average kinetic energy
• Temperature is measured on an arbitrary scale. Heat is measure on an absolute scale.
• Specific latent heat is the energy needed to melt or boil 1kg of the material.
• It is measured in J/kg
• Energy transferred = mass x SLH
• When a substance changes state, energy is needed to break the bonds that hold molecules together
• P1b) Keeping homes warm
• Double glazing reduces energy loss by conduction - the gap between two pieces of gas is filled with gas or contains a vacuum.
• Loft insulation reduces energy loss by conduction and convection
• Insulation blocks have shiny foil on both sides to reduce energy transfer by radiation
• density = mass x volume
• Energy can be transferred by conduction or convection
• Conduction is due to the transfer of kinetic energy, convection is when a gas expands when heated.
• Energy efficiency is measured in Sankey diagrams
• Payback time = cost of insulation / annual saving
• Well instulated homes are energy efficient
• Everything that transfers energu will waste some energy as heat to surroundings
• P1c) A spectrum of waves
• Wave speed = frequency x wavelength
• The frequency order of waves is: Radio, Microwaves, Infrared, Visible, Ultraviolet, X-Ray, Gamma Ray
• Diffraction depends on the size of the gap, a larger gap means less diffraction.
• P1d) Lights and Lasers
• Signals sent are almost instant
• Each method has benefits and drawbacks
• Laser light differs from white light as it is only made up of a single frequency
• When the angle of refraction is 90, the AOI is called the critical angle
• An endoscope uses light to see inside the body
• Light passes alone optical fibres. The light is then reflected, which passes another set of fibres to an eyepiece or camera.
• If the AOI is bigger than the CA, the light is reflected; this is TIR