Science light and sound

• Luminous objects


  Objects that produce their own light
• Non-luminous objects

  Objects that do not produce light but reflect it
• Light travels in straight lines
• Luminous object


  An object that gives out light
• Non-luminous object


  An object that does not give out light
• How we see a luminous object


  Light travels in a straight line directly into the eye
• How we see a non-luminous object

  Light hits the object and some is reflected into the eye
• Shadows are formed when light is blocked by an object
• Shadows always take the shape of the object blocking the light
• Transparent material


  Materials through which light can pass completely
• Translucent material


  Materials through which light can pass partially
• Opaque material


  Materials which do not allow light to pass through them at all
• Examples of transparent, translucent and opaque materials


  • Transparent: glass, water
  • Translucent: tracing paper, waxed paper
  • Opaque: wood, metals
• Light travels in straight lines from a source and bounces off objects
• Opaque materials cannot allow light to pass through
• Transparent materials allow light to pass through
• Translucent materials allow some light to pass through
• Shadows are shortest at midday and longest at the beginning and end of the day
• Drawing the position of the sun and the tree's shadow at different times

  1. 8:00 AM

  2. 12:00 PM

  3. 5:00 PM
• Cornea


  Transparent layer protecting the eye
• Pupil


  Opening in the eye which lets light in, dilates and constricts depending on light intensity
• Lens


  Focuses light on the retina
• Iris


  Coloured ring muscle which controls the size of the pupil
• Retina


  Where the image forms
• Optic nerve


  Carries electrical messages from the eye to the brain where the image is processed
• The image on the retina is inverted but the brain turns it the right way up
• Pupil in bright light


  Constricts to protect the eye
• Pupil in dim light


  Dilates to let more light in
• Sound


  Result of vibrations that make the air around the source move
• Sound travels through vibrations in the air, creating waves like a slinky spring
• Compression


  Part of a sound wave where particles are pushed together
• Rarefaction


  Part of a sound wave where particles are spread apart
• Sound travels faster in solids than liquids, and faster in liquids than gases
• Sound cannot travel through a vacuum as there are no particles for it to travel through
• Light travels faster than sound
• Examples showing light is faster than sound

  • Thunder and lightning
  • Seeing the puff of smoke before hearing the bang
• Pinna


  Outer ear that collects sound vibrations
• Ear canal


  Contains wax to prevent dust and microbes entering
• Ear drum


  Vibrates when sound waves reach it
• Ossicles


  Three small bones that vibrate when the ear drum vibrates