Miscellaneous Questions or Comments
Thu, Apr 10, 2:15 p.m. - When can we get the 3*5 card?
They're available now on the table outside the physics and astronomy office, Olin 153.
Wed, Apr 9, 6:34 p.m. - When is the review session for test 3?
It will be next Tuesday, April 15 at 8:00 pm.
Wed, Mar 19, 7:24 p.m. - Hey, I am wondering how we can determine j max? Does j max mean N is also maximum?
The number of photons in the $j$th mode goes as $1/j$. The larger $j$ gets, the smaller $N_j$ gets. But $N_j$ can't become smaller than 1, so this defines $j_\text{max}$: it's the value of $j$ at which $N_j=1$. That is, $N_{j_\text{max}}=1$.
So that is how you find $j_\text{max}$. For example, if you know $N_1=4500$, then we must have $N_j = 4500/j$ (notice that it gives the right answer for $j=1$). So now $N_{j_\text{max}} = 4500/j_\text{max} = 1$, which you can solve for $j_\text{max}$.
Wed, Mar 19, 7:21 p.m. - The question I would like to ask is in lecture 13, we learned about Eth = (0.5 kB T per mode)*(# of mode). By this formula, why can't we have infinite energy? Thanks!
The formula does predict infinite energy, but we know that this isn't what happens. Because if it did happen, we would all be cooked by the infinite EM wave thermal energy. But also, we can measure how much energy there is, and so it's a known quantity that is definitely not infinity.
What we learn from this is that the approach that led to $E_\text{th} = (0.5 k_BT \text{ per mode}) \times (\text{# of modes})$ must be wrong. It was based on assuming the EM waves were just waves and neglected the photon aspect of light. The solution is to not neglect that light is made up of photons.
Tue, Mar 18, 11:12 p.m. - Hey, I just want to have a clarification. Why can't have infinite energy?
Sorry, I'm not sure what you're asking. For what it's worth, nothing can have infinite energy because there just isn't that much energy to be had! But if I totally misunderstood your question, please try asking it again.
Tue, Mar 18, 3:45 p.m. - The calendar says there is a hand in due the monday after exam 2, is that right?
That was a mistake, and it's been corrected. Thanks for pointing that out.
Sun, Mar 16, 10:12 a.m. - Under check scores it says our course grade is an F?
That was a glitch. Thanks for bringing it to our attention and it should be fixed now.
Mon, Feb 24, 6:02 p.m. - when is the belonging survey happening?
We don't do a belonging survey in PHYS 212.
Tue, Jan 21, 12:41 p.m. - Is it possible to get the "A Typical Week in the Life of PHYS212 Student" back and posted somewhere?
That's a great idea! I've added it to the Handouts page.
Mon, Jan 20, 6:44 p.m. - is there a reading quiz for the first day of classes or just a reading assignment?
There is no reading quiz for the first class. See you tomorrow!
Wed, Jan 15, 3:05 p.m. - testing the questions page.
Yup, seems to be working.