5WACS-2
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Contents
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 to measure angle using a protractor. Yes, I'm serious. A lot of them really don't know how to use a protractor effectively. They have a vague idea, but aren't sure. Use WRK181 to check ability to measure angles.
- Emphasise the necessity of measuring between ray of light and normal. Angles are never measured between surface and ray. Use WRK182 to practice measuring angle of incidence/reflection.
- Demonstrate how virtual images are formed by reflected rays of light.
Plenary
Homework
Additional Information
Resources Required
- Pepper's Ghost
- A3 paper
- Rayboxes
- Small mirrors
- Protractors
Textbook References
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.
Skills Addressed
Safety/Hazards
Raybox gets hot during prolonged use.