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© Boardworks Ltd 2005 1 of 31 KS4 Physics Diffraction, Interference and Resonance.

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Presentation on theme: "© Boardworks Ltd 2005 1 of 31 KS4 Physics Diffraction, Interference and Resonance."— Presentation transcript:

1 © Boardworks Ltd of 31 KS4 Physics Diffraction, Interference and Resonance

2 © Boardworks Ltd of 31 Contents Diffraction, Interference and Resonance Diffraction Interference Standing waves Summary activities Natural frequency

3 © Boardworks Ltd of 31 The ripple tank A ripple tank is a device used to study the behaviour of waves, because all waves behave in a similar manner. A ripple tank produces water waves that can be reflected, refracted and diffracted. paddle vibrates to produce waves

4 © Boardworks Ltd of 31 Reflection and refraction paddle What do you think will happen if a barrier is placed in front of the water waves? If it is a plane barrier then the waves are reflected. barrier What do you think will happen if a block is submerged in the ripple tank? The change in depth of the water causes a change in speed of the waves – they are refracted.

5 © Boardworks Ltd of 31 Barrier with small gap What do you think will happen if a barrier with a gap in it is placed in front of the water waves? It depends upon the size of the gap. If the gap is smaller than the wavelength of the waves what do you think will happen? The waves are reflected by the barrier.

6 © Boardworks Ltd of 31 Barrier with wavelength-sized gap What will happen if the width of the gap in the barrier is similar in width to the wavelength of the waves? Circular waves are produced. This effect is known as diffraction.

7 © Boardworks Ltd of 31 Barrier with large gap What will happen if the width of the gap in the barrier is larger than the wavelength of the waves? The waves pass through the gap unchanged apart from slight diffraction of the waves near their ends.

8 © Boardworks Ltd of 31 Effect of diffraction… How can the teacher in the corridor hear the school band even though he isn’t in the hall?

9 © Boardworks Ltd of 31 Effects of diffraction When you are in a room, why can you hear people in the corridor even though you can’t see them? Light and sound are both waves. Waves travel in straight lines. Sound waves have a wavelength similar in magnitude to the width of the doorway and so diffraction occurs. Light waves have a much shorter wavelength than sound waves and are not diffracted by the doorway.


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