# Physics paper 2 content :)

• If two act on an object along the same line, the resultant force is
• Their difference, if the forces act in opposite directions
• Their sum, if the forces act in the same direction
• Magnetism and Electromagnet-ism
• 12.1 = The electromagne-tic spectrum
• Electromagne-tic waves
• Electric waves and magnetic disturbances that can be used ti transfer energy from a source to an absorber.
• 12.2 = Light, infrared, microwaves, and radio waves
• 12.3 = Communicati-ons
• Radio waves of different frequencies are used for different purposes because the wavelength of the waves affect:
• How far they can travel
• How much they spread
• How much information they can carry
• Microwave's are used for satellite TV signals
• Optical fibres are very thin transparent fibres that are used to transmit communication signals by light and infrared radiation
• 12.4 = Ultraviolet waves, X-rays, and gamma rays
• Ultraviolet waves have shorter wavelength than visible light
• Gamma rays are used to kill harmful bacteria in food, to sterilise surgical equipment, and to kill cancer cells.
• Ionising radiation makes uncharged atoms become charged
• X-rays and gamma rays damage living tissues when they pass through it
• 13.1 = Magnetic fields
• Like poles repel, and unlike poles attract
• The magnetic field lines of a bar magnet curve around from the north pole of the bar magnet to the south
• Induced magnetism is created in an unmagnetised magnetic material when the material is placed in the magnetic field
• Steel is used instead of iron to make permanent magnets because steel does not lose its magnetism easily, but iron does
• 13.2 Magnetic fields of electric currents
• An electromagnetic a solenoid that has an iron core. It consists of an insulated wire wrapped around an iron bar
• The magnetic field lines in a solenoid are parallel to its axis and are all in the same direction. A uniform magnetic field is one in which the magnetic field lines are parallel
• Increasing the current makes the magnetic field stronger. Reversing the direction of the current reverses the magnetic field lines
• The magnetic field lines around a wire are circles centred on the wire in a plane perpendicular to the wire
• The electromagnet-ic spectrum (in order of decreasing wavelength, increasing frequency and energy) is made of:
• Microwaves
• Ultraviolet waves
• X-rays and gamma rays
• Visible light
• 12.1 = The electromagne-tic spectrum
• Electromagne-tic waves
• Electric waves and magnetic disturbances that can be used ti transfer energy from a source to an absorber.
• Microwaves
• Used to carry satellite TV programmes and mobile phone calls
• 12.2 = Light, infrared, microwaves, and radio waves