<p>3c:
At the critical angle, the refracted angle all but disappears; it is 90 degrees, so sin(theta) = 1. So, n2 = n1sin(incident angle that results in a 90 degree refracted angle). Because you know n1 (index of refraction for air) and you can measure the incident angle, you can determine n2, the index of refraction for plastic.</p>
<p>7d:</p>
<p>Are you sure that an energy of 11ev will have no effect? Couldn’t it move the electron to an energy level that requires less than 11ev?</p>
<p>@Benjineering I wasn’t too sure about the acceleration graph. But I’m sure they’d accept any alternate correct procedure for 6b. As for 7c, it asks for the ionization energy for an electron in the ground* state, which the difference between n=1 and n=infinity is 12eV.</p>
<p>And for 7d, electrons can only move to very exact energy levels when they absorb photons with energies that are exactly equal to the difference in energy between the two states. While there is enough energy, it is too much for the n=2 state and too little for the n=3 state, so it won’t leave n=1.</p>
<p>@yayitsme, the difference between n=1 and n=2 is indeed 9eV, but to find the longest wavelength emitted, you must use the smallest energy change which is between n=3 and n=2.</p>
<p>JayAyyWhy, all of the answers you posted in the Google Doc are correct. One additional thing I would add is that in 6c, you should mention that Wire Y accelerates upward, not just moves upward. And for 6eii, the right end is at the higher potential.</p>
<p>this is really random (but important): for free response questions, is it valid to justify a response with something along the lines of “since W= -p * delta v, this is why …” or is that considered just regurgitation of an equation?</p>