physicsp2

• Name the 4 ways of increasing the strength of an electromagnet.


  1.Increase the current

  2.Increase the number of turns on the solenoid, while keeping the length the same

  3.Reduce/decrease length of solenoid while keeping the number of turns the same

  4.Add a soft iron core
• Atomic theory:


  An idea that everything is made up of tiny little particles that cant be broken down any further.- Democritus (500 BC)
• 1800- history atomic 


  John Dalton- Atoms were solid spheres
• 1897-JJ Thomson


  Plum Pudding Model-showed atoms could not be solid spheres through experiments and showed that they must've contained negatively charged particles. - atom was a geenral ball of posiitve charge with electrons
• • Ernest rutherford-Nuclear model -1909


  Positively charged alpha particles fired at a thin sheet of gold- idea if positive charge in gold was spread out then the alpha particles should pass straight through, however some alpha particles were deflected to the side or back where they were fired from. -proved Thomsons theory wrong

  -Compact nucleus w all positive charge and negative charge around the nucleus as a cloud- flaw nothing stopping cloud of negative electrons from rushing in to positive nucleus
• 1913-Niels Bohr- Nuclear model


  suggested electrons orbit nucleus, held in shells- important as orbiting of electrons prevents atom from collapsing
• James chadwick-neutrons
• Radioactive decay-unstable isotopes emit something so they can change and become stable
• 4 types of nuclear radiation

  -Beta particles

  -Gamma particles

  -Alpha particles

  -Neutrons
• Alpha radiation- 2 protons and 2 neutrons- Helium 


  -Relatively large- therefore cannot penetrate very far into other materials- least penetrating- travels a few cm in air and is absorbed by a thin sheet of paper
• Beta particle- electron-=neutron decays into a proton and electron


  -moderately ionising

  -penetrates moderately far- several metres in air, -5 mm of aluminium to stop
• Gamma rays- waves of electromagenetic radiation- emitted after b and a radiation


  -passes straight through materials- weakly ionising

  -penetrate really far

  -travels long distances

  -stopped by thick sheets of lead or multiple layers of concrete
• Emission of a neutron

  -If a nucleus contaisn too many neutron, it throws out a neutron to make nucleuus stable
• A radioactive material has unstable isotopes that can decay
• Electromagnetic spectrum 


  R-Red (Ralph) -LF LW

  O-Orange (Of)

  Y-Yellow(York)

  G-Green(Gave)

  B-Blue(Battle)

  I-Indigo(In)

  V-Violet(Vein) -HF SW
• What are waves function?

  They transfer energy from one place to another. (don't transfer any matter)
• Oscilate:


  For a wave to travel from one place to another, they vibrate
• Distance of a wave:

  How far a wave has travelled from its starting point.
• Displacement of wave


  How far from the equilibrium point the wave has oscillated
• Amplitude:


  Distance of one entire oscillation (wavelength)
• Frequency for waves - 1 (wavelength)/ time (s)
• Wave speed- Frequency x wavelength (m)
• Transverse wave facts


  -Oscillations are perpendicular to the direction of energy transfer (travelling from leftup to downright)

  -e.g. electromagnetic, light, radio, ripples/waves and waves of strings
• Longitudinal waves


  -Oscillation are parallel to the direction of energy transfer (some of the waves are more spread out and some are more compressed)

  e..g sound, and shock (siesmic p waves)
• Amplitude of a wave

  The amplitude of a wave is the maximum displacement from the equilbrium position ( x axis)
• Waves arent always reflected, what could also happen to waves?

  -Absorbed (by material) (energy transferred)

  -Transmitted (Wave enters and passes through the other side, leading to refraction.
• What 2 things does a waves contact with a material depend on?

  -The wavelength

  -The properties of the two materials
• Angle of incidence=Angle of reflection
• On mirrors the normal is always in the same direction, as it is a smooth surface- SPECULAR REFLECTION (clear image)- Boundary is flat

  On paper, the light is reflected in different directions, so the normals will all be different.- Boundary is bumpy- DIFFUSE SCATTERED
• What does refraction of light waves mean?

  Waves change direction as they pass from 1 medium to another.
• The higher the density of the medium (material)= then the slower the wave (E..G A wave moving from a less dense medium like air to a more dense medium like glass, the wavelength will be slower.

  If the wave is travelling perpendicular to the boundary, like the two materials, then it will continue straight on.

  However if a wave hits at an angle, it will be refracted (its direction will change)- if its passing into a more dense medium. it will bend towards the normal.
• If the speed of a wave increases, the wavelength must increase as well, frequencies stay the same
• Refraction refers to the change in direction of a wave, as it passes from one medium to another, and is caused by its change in speed
• Light travelling from a less dense material, into a more dense material, will bend towards the normal.
• Electromagnetic waves have certain thing in common:

  1-Transverse waves- their oscillation is perpendicular to the direction of energy transfer.

  2. Their wavelength and frequency is inversely related (so if one was to increase, the other would decrease)
• Electromagnetic spectrum


  R-radio waves (longest wavelength, lowest frequency) - 10^4m-1m

  M- micro waves -10^-5m

  I - infrared - 10^-7

  V -visible light

  U -Uv light -10^-8

  X -X ray-10^-10

  G - Gamma rays (shortest wavelength, highest frequency) -10^-15
• Radioactive decay can cause gamma rays to be emitted

  Visible Uv and Xray are all emitted when electrons drop down energy levels

  Infraered is emitted when the bonds holding molecules together vibrate
• Name 3 examples of scalara quantities

  -Distance

  -Temperature

  -Speed
• Examples of vector quantities

  -Weight

  -Displacement

  -Velocity
• In a free body diagram the arrows of:

  Forward arrow represents the thrust

  The backward arrow represents the air resistance

  Downward arrow is the weight

  And the upwards arrow is the lift