Light

• Light travels as a transverse wave
• Draw a transverse wave


  Add two labelled arrows to your wave: one to indicate the direction of energy transfer and one to indicate the direction of oscillation
• States of matter light can travel through

  • Gases
  • Liquids
  • Some solids (like glass)
• Vacuum


  Completely empty space with NO particles! Not even air!
• Light can travel through vacuums which means it can travel through space
• Light travels 300,000km/s
• Light-time


  Used to measure distances in space
• 1 light-minute is how far light can travel in 1 minute
• 1 light year is the distance light can travel in 1 year
• Light


  Travels faster than sound
• Venn diagram comparing light and sound

  • How fast they travel
  • What states of matter they can travel through
  • What type of wave they are
  • What they are used for
  • Can they travel through space
  • Do they need particles to travel
• Light travels at 300,000km/s
• Sound travels at 340 m/s
• Light and sound can both travel through liquid and gas states
• Light can travel through some solids, sound can travel through all solids
• Light is a transverse wave, sound is a longitudinal wave
• Light is used to see and tell distances in space, sound is used for communication and forming images of things we can't see
• Light can travel through space, sound cannot
• Light does not need particles to travel, sound needs particles to travel
• Both light and sound travel as waves and spread out as they get further from the source
• We need light to see everything
• How we see non-luminous objects

  1. Luminous objects emit light

  2. Light reflects off non-luminous objects

  3. Our eyes absorb the reflected light
• Types of objects based on how they interact with light

  • Transparent (transmits all light)
  • Translucent (scatters light as it passes through)
  • Opaque (transmits no light)
• Transmit


  When light passes through an object
• Light is absorbed by water even though you can see through it. Only a small amount is absorbed, so you need a lot of water for it to become dark at the bottom of the ocean
• Measuring the brightness of light

  1. Hold the light source 5–10 cm from the light meter

  2. Arrange the cardboard to block out all light except the light from the light source

  3. Measure the light intensity with nothing between the light source and the light meter

  4. Slide a material to be tested between the cardboard and the light meter

  5. Measure the light intensity

  6. Repeat for each material
• Independent variable


  The variable that is changed or controlled in a scientific experiment to observe its effects on the dependent variable
• Dependent variable


  The variable that is measured or observed for changes in a scientific experiment
• Control variable


  A variable that is kept constant to ensure the validity of the experiment
• The cardboard shield was necessary to use in this investigation to block out all light except the light from the light source
• Emitting light


  When an object produces its own light
• Transmitting light


  When light passes through an object
• Describe the journey that light takes from the sun to your eye when you are looking at fish in a pond

  Use diagrams to illustrate your answer