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Can someone help me with this please?
B(f) = [(2hf^3)/c^2]{1/[exp (hf/kT) - 1]} - Planck law in terms of frequency.
"Derive expressions for B(f) for the cases i. hf << kT, ii. hf >> kT".
I've done the first bit, that's just using a Taylor expansion. The second bit is where I'm stuck. In my lecture notes, I have that for hf >> kT, B(f) = [(2hf^3)/c^2]exp(-hf/kT). What I don't understand is why it's like that. If hf >> kT, shouldn't that exponential tend to infinity?
Thanks.
B(f) = [(2hf^3)/c^2]{1/[exp (hf/kT) - 1]} - Planck law in terms of frequency.
"Derive expressions for B(f) for the cases i. hf << kT, ii. hf >> kT".
I've done the first bit, that's just using a Taylor expansion. The second bit is where I'm stuck. In my lecture notes, I have that for hf >> kT, B(f) = [(2hf^3)/c^2]exp(-hf/kT). What I don't understand is why it's like that. If hf >> kT, shouldn't that exponential tend to infinity?
Thanks.
.