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Δp for total reflection and absorbtion of E&M radiation explanation?

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Phyzwizz
#1
Apr18-13, 11:43 AM
P: 54
The equation for the change in momentum for total absorption of electromagnetic radiation is ΔU/c and that for total reflection is (2ΔU)/c. How could the momentum of electromagnetic radiation change if it is massless and travels at a constant speed c? Is the ΔU just a representation of a change in the frequency of the radiation? Also my book does a poor job in explaining the reason that the change in momentum is double for total reflection (perhaps this will become more clear with an explanation of the previous questions).Δ
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technician
#2
Apr18-13, 12:46 PM
P: 1,506
The change in momentum for reflection is 2 x thechange for absorption for the same reason that the change in momentum for a ball hitting a wall and stopping dead is mv but a ball rebounding with the same speed has a change in momentum of 2mv. Momentum changes from +mv to -mv.
virtuosowanaB
#3
Apr21-13, 01:07 AM
P: 6
Complete Reflection

Δp = ΔU/c - (-ΔU/c) = 2(ΔU/c)


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