00:01
So this is a question about the cosmic background radiation that we see emanating from the big bang remnants.
00:09
And it goes by another name, but that's going to be giving away the answer.
00:14
So first, we want to figure out what the wavelength, peak wavelength is for the radiation emitted by this process.
00:27
And so we can use that hf, f, is less than or approximately equal to kbt for thermal radiation.
00:36
And what that means is that, and these are both right in units of energy.
00:45
So this is units of energy.
00:48
And so we know that e equals hf, which equals hc over lambda.
00:58
So we can use this to find our peak wavelength.
01:03
So first we want to find what kbt is to get our energy.
01:08
So energy of these photons is going to equal kb times t, where kb is boltzman's constant.
01:20
And in units of electron volts, it's going to be 8 .617 times 10 to the negative fifth electron volts for kelvin.
01:31
And so our energy is going to equal 8 .617 times 10 to the negative 5th electron volts per kelvin times 2 .7 kelvin.
01:47
It's very cold...