igcse physics part 2
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Physics IGCSE Revision(Part 2)
By: Momina
Key pointsFormulae
Simple Easy
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Sound Waves-Describing themAmplitude
Wavelength
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Transverse Waves
• The oscillations are at right angles to the direction of the wave.
• For example light waves.
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Longitudinal Wave
• It consists of compressions and rarefactions.• Oscillations are in direction of travel.• For example: Sound waves.
( Rarefactions)
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The Wave Equation
Speed wavelengthFrequency= x
V f= x
= Lambda
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Wave Effects: Reflection
The waves are reflected from the
surface at the same angle they hit it.
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Wave Effects: Refraction
Due to the plastic the water becomes
shallower causing the waves to slow down. This effect is called
refraction.
Plastic
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Wave Effects: Diffraction
• Diffraction is when the light bends around obstacles.
• Wider gaps produce less defraction.
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Sound waves• Sound waves are caused by vibration• Sound waves consist of Longitudinal waves.
- Compression passes Air pressure increases-Rarefaction passes Air pressure decreases
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Sound Waves
• Sound waves need a medium to travel in. For instance the air.
• Sound waves can also be diffracted due to their long wavelength.
• They can be displayed on an oscilloscope. The sound enters via the microphone, a metal plate vibrates, these vibrations cause electrical oscillations producing a wave front.
IT IS NOT A PICTURE OF THE
SOUND WAVE BECAUSE SOUND WAVES ARE NOT
TRANSVERSE
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Speed of Sound
• Temperature of air: Sound travels faster through hot air.
• Does NOT depend on pressure: the pressure may change but the speed of the wave will remain the same
• The speed of sound is different through different materials.
Ultrasound: sounds above the range of human hearing.
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How to Measure the speed of an echo?
You could use:- Echo-sounder- Electronic tape measure (Works like an echo-sounder)- Radar
Speed Time
Distance=
To measure echoTake note here the distance is the distance from to the wall and then BACK !
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Features of Light
1. Form of radiation2. Travels in straight lines3. Transfers energy4. Transverse waves5. Can travel through vacuum6. 300,000 m/s
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Law of reflection
• i˚=r˚• i, r and normal lie on the same plane.
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Total Internal Reflection
• Anything greater than the critical angle does not have a refracted ray. Which means that all the light is reflected thus leading to TOTAL internal reflection.
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Lenses
Convex Lens Concave Lens
Convex lenses are used in projectors as they form large, inverted, real images on the screen
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When the object is less than F1
Original ObjectRefracted Object
Refracted image is -Upright-Larger-Virtual
-It is also on the same side as F1
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When the object is at 2F1
Refracted image is -At 2F2-Inverted-The same size-Real
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When the Object is between F1 and 2F1
Refracted image is -Beyond 2F-Inverted-Larger-Real
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When the object is beyond 2F1
Refracted image is -Between F2 and 2F2-Inverted-Smaller-Real
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The Electromagnetic Spectrum
Electromagnetic waves are emitted when a charged particle oscillate or loose energy in some
way.
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Electricity
• Rubbing materials does not MAKE charge, it only separates charges that are already there.
• Induced charge: this is the charge that ‘appear’ on an uncharged object because of the charged object nearby.
Charge is measured in Coulombs.
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Electricity*
• Electrostatic precipitators: are fitted into chimneys in order to reduce pollution
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Electricity
• When there are no ions in the air it is a good electrical insulator.
• When there are ions present in the air it is a good conductor
Current is measured in amps.
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Current
• Current remains the same at all points round a simple circuit.
Charge TimeCurrent= x
Conventional Current flows from positive to negative.Electron flow is from negative to positive.
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Potential Difference (Voltage)
• The highest potential difference is when it is not in a circuit and it not supplying current. This is also known as the Electromotive force.
• In a simple circuit, the sum of the PD’s across the components is equal to the PD across the battery.
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Resistance
ResistanceCurrent (A)
PD (Voltage)=
RI
V=
Ohms LawThe current is proportional to the PD.
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How can resistance be increased?
1- Length : Doubling the length increases resistance
2- Cross-sectional area: halving the surface area. (thin wire is more resistance than a thick one)
3- Material4- Temperature: resistance increases with
temperature
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CIRCUIT WARS!
Parallel Circuit- Gets full PD from the battery- One bulb removed the other
still works- Total current = Sum of the
currents in the branches.- Resistance:
Simple Circuits- Bulbs share PD- One bulb removed, the
other one goes out.- Current through each
component is the same- Resistance:
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CIRCUIT WARS!
Parallel Circuit Simple Circuits
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Power
PowerTime take
Work done=
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Power
Power VoltageCurrent= x
P VI= x
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Power
Power ResistanceCurrent= x
P VI= x
2
2
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Electrical Energy Equation
Energy Transformed
TimePD= xCurrentx
E tV= xIx
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In Progress….
• Part three of this series still remains a work in progress..
Part 3 will contain:- Magnets and Currents- Electrons and Electronics- Atoms and Radioactivity