Ill put some notes for the light topic .
Notes
hysics waves/energy/light
Energy and Waves
Energy: The ability to do work. Work = Force x Displacement. Energy can be neither created, nor destroyed.
Types of Energy:
Light, Heat, Sound, Kinetic, Solar, Nuclear, Chemical, Potential, Geothermal, Electrical, Elastic, Gravitational. Some sources of energy are:
• Fossil Fuels
• Wind/Solar/Tidal
• Radioactive materials
• Food
Waves: A distortion in a medium or material where the individual parts of the material cycle back and forth, or up and down, but the wave itself moves through the material.
Transverse Waves
An up and down motion, for example:
A vibrating guitar string
Electromagnetic/Light waves
A mexican wave (Good old Mrs. Walker)
Compression Waves
A back and forth motion, for example:
Sound waves
A stretched slinky
AC electricity (Electrons move back and forth in a wire sending a wave of electric current down the wire)
Physics
The Wave Model
• Wave length => distance between crests or ‘bumps’
• Frequency => The number of cycles that pass a given point per second
• Transverse Waves => Particles move up and down
• Longitudinal Waves => Particles move side-to-side
• [Order of sizes of waves] Gamma => X-rays => UV => Visible => Infrared => Microwaves => Radio
• Gamma rays kill cancer cells
• X-rays can penetrate the flesh but not the bone, to enable the user to indentify broken bones
• UV rays kill bacteria
• Visible light allows people to see, during the day and night
• Microwaves can use satellites to communicate around the world
Light Energy
• White light is made up of all the colours of the rainbow
• Absorption => Light is ‘absorbed’ by the surface (black absorbs all colours)
o E.g. Green paper; would absorb red, orange, yellow, blue, indigo and violet, and only reflect green light into our eyes
• Reflection => Angle of incidence = Angle of reflection
o E.g. Mirror; if you look into the at 45°, you would be able to see up to 90° from where you are standing
• Refraction => Bends the light through a certain material (e.g. glass)
o E.g. A glass filled with water would bend light, as the light must travel through it to reach the other side