Diffraction Lesson Plan

Light is everywhere in our world. We need it to see: it carries information from the world to our eyes and brains. Seeing colours and shapes is second nature to us, yet light is a perplexing phenomenon when we study it more closely.

Here are some things to think about:

 

  • Our brains and eyes act together to make extraordinary things happen in perception. Movies are sequences of still pictures. Magazine pictures are arrays of dots.

     

  • Light acts like particles—little light bullets—that stream from the source. This explains how shadows work.

     

  • Light also acts like waves—ripples in space—instead of bullets. This explains how rainbows work. In fact, light is both. This "wave-particle duality" is one of the most confusing—and wonderful—principles of physics.

Scientists have spent lifetimes developing consistent physical, biological, chemical, and mathematical explanations for these principles. But we can start on the road to deeper understanding without all the equations by acting as scientists do: making observations, performing experiments, and testing our conjectures against what we see.

The activities in this lab are designed to give you ideas about light—and also about how you can use technology to explore light. Collectively, the activities are a sampler—rather than comprehensive demonstration—of these two topics:

 

  • Light in Colour. Colour is more than decoration, and perceiving color is tricky. Three activities help you see how colours interact and how we can use colour as a scientific tool.

     

  • Laws of Light. Light behaves according to special rules; for example, it usually travels in a straight line and it bounces off mirrors at the same angle it hits them.

In this lab, you will work with simulations to see things more quickly and conveniently. This has merit, but it's no substitute for the real thing.

 

This is a 15 - 20 minute resource that has been used for both KS1 and KS2 children. As long as the enquiry based learning methodology is used the lesson will find its own level. Children of all skills and abilities will be enthused and motivated by this simple to prepare and pleasure to deliver lesson plan.  Certain errors in original submission amended with kind assistance from Andrew Urwin. Park School.

 

Materials

  • Education Harbour Rainbow Glasses
  • Light Source (a wind up torch).

Procedure

  1. Prepare the glasses ready to hand out to the children. Make sure nobody tries them on until you say so.
  2. Show the children your wind up torch and ask them if they know what it is and what it does.
  3. Affirm that the torch uses energy from you and converts that to electricity and which is then converted to light energy.
  4. Wind the torch slowly and ask them what the colour the light is. The answer that you are looking for is ‘yellow’
  5. Wind it up as fast as you can and ask what colour the light beam is now. The answer that you are now looking for is ‘white’.
  6. This should begin to suggest that there is a relationship between energy and colour.  
  7. Ask them to name any other forms of yellow or white light.
  8. Ask them to decide which is the brightest form of yellow/white light that they can think of. The answer will be ‘the sun’.
  9. Explain to the children that white light coming to us from the sun contains all the colours that we see in our day to day lives. Ask what colours can be seen at night when it is dark and the sun is not shining?
  10. Ask the children if they can think of any times when the nature shows us that the sunlight is made up lots of different colours? While they are thinking hum the tune to ‘Somewhere over the rainbow’ or play it on the class music system if your humming is not good.
  11. Ask if anyone can name all of the colours of a rainbow in the correct order.
  12. Red, Orange, Yellow, Green, Blue, Indigo, Violet
  13. Red light has the lowest energy and violet the highest energy. UV is too high in energy (short wavelength) to see.
  14. There are a few simple ways to remember the order:

    -       ROY G BIV

    -       Richard Of York Gave Battle In Vain

  15. Mix up between SUBTRACTIVE(Paint)and ADDITIVE(light)colour mixing.For mixing coloured LIGHT:primary colours red GREEN & blue. Secondaries: R+G=Yellow, R+B=Magenta B+G=Cyan.
  16. Rainbows caused by raindrops acting as tiny prisms which REFRACT light. Refraction is when light bends as it goes THROUGH something transparent. DIFFRACTION is the spreading out of light waves as they passs through tiny apertures.So rainbows, Newton,prisms= refraction;colours on CDs,oil on puddles and your glasses=diffraction(prob too difficult for primary school (A-level). 17.  The word, and scientific concept  of ‘diffraction’ was introduced to us by Francesco Maria Grimaldi some time around the mid seventeenth century from the Latin word ‘diffringere’ which means ‘break into pieces’.
  17. Between 1670 and 1672 Sir Isaac Newton also studied this same effect by looking at the sunlight shining on raindrops on his window.
  18. Would you all like to see exactly what Francesco and Sir Isaac saw but without waiting for sunlight to shine on raindrops?
  19. All I need is my wind up torch again and all you need is to wear a pair of these Diffraction Glasses that I am going to hand out now.
  20. To ensure that they work well for you, do not put them on until I say so.
  21. Turn off the classroom lights and, if practical, close the blinds/curtains.
  22. Wind up the torch and ask them to put the glasses on.
  23. Make sure that they all say ‘ooh’ in harmony.
  24. Light up a second torch, a candle or other local light sources and listen for more oohs.
  25. Explain that the the glasses and raindrops split light in different ways (see above). The spectrum produced is the same..
  26. Turn the classroom lights back on and the children will see for certain that it was not your special light; the concept of diffraction works with almost any light.
  27. Collect up the glasses and summarise. Explain to the children that white light coming to us from the sun contains all the colours that we see in our day to day lives. Ask what colours can be seen at night when it is dark and the sun is not shining? Ask the children if they can think of any times when the nature shows us that the sunlight is made up lots of different colours? While they are thinking hum the tune to ‘Somewhere over the rainbow’ or play it on the class music system if your humming is not good. Ask if anyone can name all of the colours of a rainbow in the correct order. Red, Orange, Yellow, Green, Blue, Indigo, Violet and all the colors in between) when you look through your Education Harbour Rainbow Diffraction Grating Glasses. There are two colour ranges that are not visible to our eyes in this spectrum: below red is infra-red and above violet is ultra-violet. In a rainbow after a rainstorm this same colour spectrum appears in the same order. Rainbows are created when sunlight passes through rain drops that act as millions of tiny prisms.

      

    The colour of a solid object depends on the colours of light that it reflects. A red object looks red because it reflects red light and absorbs all other colours. A blue object looks blue because it reflects blue light and absorbs all other colours. A white object reflects all colours of light equally and appears white. A black object absorbs all colours and reflects no visible light and appears black. Just like when you colour with too many colours in one area with crayons or markers, all colours are absorbed, none are reflected and it appears black!
  28.  

Ends:

 

Other ideas to reinforce learning:

 

  • Newton’s Colour Wheel
  • Colour Filters to make things disappear
  • Primary Colours
    • The primary colours are red, blue, and yellow.  The secondary colours are combinations of the primary colours.  For example if you mix blue and red, you get purple; if you mix red and yellow, you get orange, and if you mix yellow and blue, you get green.  These are the secondary colours.  If you then mix a secondary colour with a primary colour, you will get another set of colours called tertiary colours.  You can see what colours they are by using the colour wheel.

 

Absorb:  When light does not bounce off a surface, so that it does not return to our eyes and we cannot see it.

 

Black:  We see black when white light (or all the colours of light) hits a surface and is absorbed, leaving nothing to reflect back into our eyes.

 

Colour:  Different colours are made of different wavelengths vibrating at different speeds.  We see a colour when white light hits a surface, and a particular colour is reflected back into our eyes (such as green being reflected off grass), the other colours being absorbed at the same time.

 

Light Spectrum:  An arrangement of light rays according to wavelengths.

 

Primary Colours:  Red, yellow and blue.

 

Reflect:  When light bounces off a surface to return to our eyes so that we can see it.

 

Secondary Colours:  Produced by mixing any two of the three primary colours.

 

Tertiary Colours:  Produced by mixing one primary colour with one secondary colour.

 

Ultraviolet “Black” Light:  A colour we cannot really see.  It is at the end of the visible spectrum after violet.  It kills bacteria and is the main ingredient in a summer tan.

 

Visible Spectrum:  The part of the light spectrum that we can see.