1. Core Physics – Energy L/O :- To understand diffraction Diffraction Exam Date -

2. Quick Quiz - What do you remember from last lesson? Draw and label a wave What is the law of reflection? What is the equation for working out the speed of a wave? What happens to a light ray when it travels from air through glass? Why does this happen? What is the equations for working out efficiency? What are the 2 different types of wave? Give an example How do you work out the pay-back time for insulation? What are the pros and cons of wind energy? Where are step-up transformers used? How does increasing the volume of a sound affect the wave?

3. What is happening in this picture? If sound and light are both waves. why can you hear around a corner but not see round it?

4. 11/11/2015 Wave behaviour 1) Reflection 4) Diffraction3) Refraction 2) Refraction

5. 11/11/2015 Diffraction More diffraction if the size of the gap is similar to the wavelength More diffraction if wavelength is increased (or frequency decreased)

6. http://www.falstad.com/ripple/ Virtual Ripple Tank

7. 11/11/2015 Sound can also be diffracted… The explosion can’t be seen over the hill, but it can be heard. We know sound travels as waves because sound can be refracted, reflected (echo) and diffracted.

8. 11/11/2015 Diffraction depends on frequency… A high frequency (short wavelength) wave doesn’t get diffracted much – the house won’t be able to receive it…

9. 11/11/2015 Diffraction depends on frequency… A low frequency (long wavelength) wave will get diffracted more, so the house can receive it…

10. 11/11/2015 Interference Interference is seen when two waves of the same type cross:

11. Interference When 2 waves meet, they interfere with each other. If they meet each other exactly in phase, the amplitudes ‘add up’ to produce large crests and troughs. += This is called constructive interference.

12. If they meet each other exactly out of phase, the amplitudes ‘subtract’ to produce no peaks or crests. += This is called destructive interference. Interference

13. 11/11/2015 Interference Patterns from 2 slits Intensity Distance Constructive interference Destructive interference

14. How could you test your prediction? What will you record? Design a table What type of graph should you use to represent your data? How could you check the reproducibility Can you work out the refractive index? Refractive index = sin i sin r

15. What have you learnt? Do you know what diffraction is? Can you predict how these waves would behave?