<p>I have a few physics b questions that I do not understand. Can someone please explain them to me? Thanks.</p>
<p>Question:
If the separation between the plates of an isolated charged parallel-plate capacitor is increased slightly, which of the following also increases?
a. the capacitance
b. the stored electrostatic energy
c. the force of attraction between the plates
d. the magnitude of the charge on each plate
e. the magnitude of the electric field in the region between the plates</p>
<p>I do not understand how the answer is b. Isn't stored electrostatic energy potential stored energy of capacitance (U=1/2cv^2)? I don't see any way where that would increase in this situation.</p>
<p>Question:
Two monochromatic light beams, one red and one green, have the same intensity and same cross-sectional area. How does the energy of each photon and the number of photons crossing a unit area per second compare with those of the green beam?</p>
<p>A.) Energy of photon = Same, Number of photons crossing per unit area per second = same
B.) Energy of photon = Greater for red, Number of photons crossing per unit area per second = Less for red
C.) Energy of photon = Greater for red, Number of photons crossing per unit area per second = Greater for red
D.) Energy of photon = Less for red, Number of photons crossing per unit area per second = Less for red
E.) Energy of photon = Less for red, Number of photons crossing per unit area per second = Greater for red</p>
<p>I understand that the energy for the photon is less because the frequency of the red beam is less than the green beam. I don't understand how the number of photons crossing per unit area per second is greater for red. If intensity is the same, shouldn't the number of photons be the same? In that case the number of photons crossing per unit area per second should be the same.</p>