5WACS-2

Outcomes

• Pupils can use a raybox.
• Pupils can define the term 'reflection'.
• Pupils understand the law of reflection.

Specification References

• 3.14 recall that light waves are transverse waves which can be reflected, refracted and diffracted
• 3.15 recall that the angle of incidence equals the angle of reflection

Starter

• Pupils to write down the names of all the parts of the raybox that they can remember. Check what they remembered:
  • Power supply
  • Bulb
  • Lens
  • Slit(s)
  • White paper (this now counts as part of a raybox)

Main Body of Lesson

• Explain to pupils that when light strikes a surface, three things (or a combination thereof) can happen:
  • Absorption (e.g. blue light on a red surface)
  • Transmission (e.g. light through glass)
  • Reflection (e.g. image formation by a mirror)
• Be careful to note that there is usually a combination of processes: light hitting glass is not 100% transmitted - a small portion is reflected.
• There is a good opportunity here to talk about "one-way mirrors" and to demonstrate the effect of light levels on reflection with Pepper's Ghost. Another good example is train carriages: during the day you see out, during the night you see a reflection of the carriage's interior.
• Question pupils on what the "rules" governing reflection are likely to be. One will doubtlessly get the idea of angle of incidence = angle of reflection, but not in those words.
• Give pupils the "official" form of the law of reflection angle of incidence equals the angle of reflection
• Revise how to use a raybox. Remind pupils to tape down an A3 sheet of paper before starting.
• Revise how to draw the normal to a surface.
• Pupils use raybox and small mirror to create three lines of incidence and three lines of reflection (in different colours).
• Demonstrate how virtual images are formed by reflected rays of light.

Additional Information

Resources Required

• Pepper's Ghost
• A3 paper
• Rayboxes
• Small mirrors
• Protractors

Website References

• Gorillaz and Madonna used Pepper's Ghost at the Grammy's a few years ago: http://www.youtube.com/watch?v=6_gnMOom7kE.

Safety/Hazards

Raybox gets hot during prolonged use.