Physics Paper 2

• Electromagnetic waves

  Types of electromagnetic waves

  Electromagnetic spectrum

  The continuous range of wavelengths and electromagnetic waves

  Electromagnetic waves are grouped according to the wavelength and frequency

  All electromagnetic waves are transverse oscillations are perpendicular to the direction of energy transfer
• Properties of Electromagnetic Waves

  Radio waves can be produced by oscillations in electrical circuits

  X-rays = Used to make images of bones

  Gamma rays: Used to destroy cancer cells through ionisation

  Risks: Ionising radiation causes mutation of genes by altering DNA which can cause cancer.
• Ionising radiation

  Electromagnetic waves with enough energy so they can knock off electrons off atoms, making atoms into charged ions
• Refraction and wave front diagram

  A wave bends towards the normal, when it slows down.

  A wave bends away from the normal when it speeds up

  If a wave changes medium at normal, so it slows down and no refraction.
• Electromagnetic Waves in Communication

  Signal

  A signal is an observable change in a quality that carries information. A signal enables communication.

  An upload signal is transmitted from a transmitter to a satellite.

  A download signal is then transmitted from the satellite back to the receiver.
• Electromagnetic Waves in communication 2

  Mobile phones:

  • A band of frequencies in microwave

  Infrared:

  • "Line of Sight"
  • Moisture reduces range of infrared signal

  Bluetooth:

  • Short wavelength signals
  • "Frequency hopping" to reduce interference with Wifi

  Wifi:

  • Frequency region up to 100m
• Infrared Radiation

  Electromagnetic waves that are invisible to the human eye, but we can feel as heat

  Independent variable = Colour of container

  Dependent variable = Temperature of the container

  Control variable = Same amounts of hot water
• Magnets and Magnetic Field

  Magnets

  A magnet has two ends. These are called the north and south poles. Magnets exert a non-contact force.

  Two types of magnets:

  Permanent

  Induced

  A magnetic field is a region around a magnet where the non-contact force acts on another magnet
• Solenoid

  A coil of wire with current passing through it, which creates a magnetic field
• Electromagnets

  An insulated wire wrapped around an iron core which becomes magnetic when there is current in the wire.

  • The strength of the magnetic field depends on the current through the wire and the distance from the wire.
  • Adding an iron core increases the strength of the magnetic field created by a current.
• The motor effect and Hand rules

  An electric motor works because a force can act on a wire in a magnetic field. When a current is passed through the wire. This is called the motor effect.

  Fleming's left hand rule shows how the direction of wires movement in relation to the direction of current and magnetic field lines.