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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Physics => Topic started by: fredrick on October 15, 2008, 03:02:10 pm

Title: Diffraction
Post by: fredrick on October 15, 2008, 03:02:10 pm

Im getting confused with the amount of diffraction of sound and of light.

For light $\frac{\lambda}{w}=1$ Means diffraction occurs, how about if that ratio was above 1 or below 1, how significant is the diffraction relative to when the ratio =1. And is it the same for diffraction of sound?

Title: Re: Diffraction
Post by: dcc on October 15, 2008, 03:48:26 pm

For electromagnetic radiation:

$d \propto \frac{ \lambda}{w}$ , where $d$ is the amount of diffraction. For significant diffraction to occur, $d \geq 1$ should be true. As $d$ decreases, the amount of diffraction gradually decreases.

This was emphasised in last years assessment report (http://www.vcaa.vic.edu.au/vce/studies/physics/assessreports/2007/physics2_assessrep_07.pdf), which stated:

Quote from: VCAA

Some areas of concern from this exam included:
the distinction between diffraction as it applies in ‘Interactions of light and matter’ compared with ‘Sound’
the gradual change in diffraction patterns as the λ/w ratio is varied

Sound (I believe) is very much the same, however the focus of the Sound unit is slightly different to Light & Matter, so it depends upon the question I suppose. (i.e. for single slit diffraction, the distance between 'bright' regions increases as diffraction increases, whereas a sound wave diffracting allows sound to be heard around 'corners' lol)