Physics Revision

Pregunta	Respuesta
What is frequency and how is it measured?	The number of complete waves passing a point in 1 second. Frequency is measured in Hertz (Hz)
What is Specific Heat Capacity?	The amount of energy needed to change the temperature of 1kg of a substance by 1 degree Celsius.
What is conduction?	The transfer of heat energy where vibrating particles pass on extra kinetic energy to neighbouring particles.
Where does conduction occur?	Mainly in solids as the particles have to vibrate against each other.
What is convection?	Convection occurs when energetic particles move from a hotter region to a cooler region - taking their heat energy with them.
Where does convection occur?	In liquids and gases as the energy has to be able to move from one region to another.
How does insulation stop convection from occurring?	By trapping pockets of air. The air then cannot move so the heat can only transfer slowly by conduction.
How do you measure Speed, Time & Distance?	Image: Speed__Time__Distance.gif (image/gif)
Image: Speed_Time_Graphs_filled (image/jpg)	Image: Speed_Time_Graphs.gif (image/gif)
Wave Speed, Frequency, Wavelength Calculation	Image: wave_speed__triangle (image/png)
What is the Amplitude?	The distance between the rest position and the crest of the wave.
What measurements are Wave Speed, Frequency and Wavelength given in?	Wave Speed = m/s Frequency = Hz Wavelength = m
What is the similarity between the Angle of Incidence and Angle of Reflection?	They are exactly the same.
What is TIR?	Total Internal Refraction
When does refraction occur?	When a wave passes into a substance of a higher or lower density.
What is the Critical Angle?	If the angle of incidence is greater than the critical angle, the rays of light internally reflect (TIR).
What is the effect of diffraction when a wave passes through different sized gaps?	Image: Diffraction (image/jpg)
What is the difference between Heat and Temperature?	Heat is a measurement of energy. Temperature is a measurement of hotness.
What will cool faster? A warm cup of tea or a hot cup of tea? Why?	The hot cup of tea because the greater the difference in temperature, the faster the rate of cooling.
What is radiation?	The transfer of heat energy in the form of Infrared Waves.
How is radiation different to conduction and convection?	It doesn't need a medium to travel through. This means heat can transfer through a vacuum.
What type of substance is the only way radiation can travel?	Clear substances such as air, glass and water.
What colour is the best at emitting and absorbing radiation?	Matte black/Dark colours
What colour is the worst at emitting and absorbing radiation?	Light-coloured, Smooth and Shiny.
What is the difference between digital and analogue signals?	Digital signals are discontinuous - either ON or OFF (0 or 1). Analogue signals are continuous - can be any value.
What is the advantage of a digital signal?	Digital signals have reduced interference as it is easier to ignore or remove 'noise' so the signal stays high quality.
What is interference?	When two or more waves of similar frequency meet and create one combined signal with a different amplitude.
What does a thermogram show?	A coloured picture of how hot an object is.
Why is a thermogram useful when installing insulation in the home?	You can look at a picture of a house and work out where the most heat is lost (and needs insulation).
How do light signals travel through optical fibres?	Bounce off the sides.
What are the different types of seismic waves?	P-waves and S-waves
Are P-waves Longitudinal or Transverse?	Longitudinal
Are S-waves Longitudinal or Transverse?	Transverse
What is meant by longitudinal?	The vibrations are along the direction the wave travels.
What is meant by Transverse?	The vibrations are at right angles to the direction that the wave travels.
What do P-waves travel through?	Liquids and solids.
What do S-waves only travel through?	Solids
Which is faster, P or S waves?	P-waves
What causes refraction?	As a wave passes through substances of different densities it changes speed. This causes the wave to change direction.
Name 3 uses of lasers.	Laser light shows, in weaponry - laser guided missiles & in manufacturing - super heated lasers/laser cutting metals.
What does LASER stand for?	Light Amplification by Stimulated Emission of Radiation
What does monochromatic mean?	A single colour.
What is meant by a laser being coherent?	They are the same frequency and are in phase with each other.
How do CDs work?	The shiny side contains billions of microscopic pits, in a spiral track, that hold digital data. The laser light is reflected off the surface of the CD as the disk spins and is detected by 1) The change in the amount of reflected light caused by entering or leaving a pit is interpreted as a 1. 2) No change in the amount of reflected light is interpreted as a 0.
How do Microwaves and Infrared Radiation cook food?	Infrared: Infrared radiation is absorbed by all particles on the surface. Microwaves: Microwave radiation is absorbed by water particles, both on the surface and up to about 1 cm deep into the food. The kinetic energy is transferred to the centre of the food by conduction or convection.
Why do microwave receivers have to be in the line-of-sight of the transmitter?	Because microwaves cannot diffract.
What may interrupt microwave signals?	Microwaves may be blocked by large buildings and other obstacles. Poor weather and surface water scatter signals. Signals may also interfere with each other.
What are some uses of microwaves?	Satellite communications and mobile phones.
Name 3 ways you could modify a house to prevent heat loss.	Loft insulation, double-glazing, cavity wall insulation.
Do all electromagnetic waves travel at the same speed in a vacuum?	Yes
Name the seven types of electromagnetic wave that make up the spectrum (in ascending order of frequency).	Radio, micro, infrared, visible light, ultraviolet light, X-ray, gamma ray
Why are people worried about microwaves?	High doses many cause cancer.
What problems can exposure to UV rays cause?	Suntan, sunburn, skin cancer, premature skin ageing.
What are CFCs doing to the Ozone layer? What are the effects of this?	CFCs make a whole in the ozone layer – which means more harmful UV rays can some in to Earth.

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