As for how to develop those skills, which I would guess is really your underlying question... I have no idea. I suppose you could practice applying your knowledge from one class to another but that might turn catastrophic if you apply things wrong.... I guess one thing I would say is to not be afraid of being wrong and when in doubt, assume. For example, if you have a question asking you which is higher energy -- red or blue -- you probably cannot do this intuitively (unless you already know the answer). However, if I asked you which is a higher energy sound wave -- a high or low pitched one -- you could probably answer that. (If not, which one hurts more? Does a higher or lower energy punch in the shoulder hurt more? Now assuming these are equivalent in terms of pain, which sound is going to hurt more? Higher energy/higher pitch, of course.) So if sound hurts more at a higher pitch/frequency and higher frequency means shorter wavelength, then what would we expect from light? (As I said, assume they are equivalent until told otherwise. This does not always work, but in many cases, such as this one, assumptions like this can actually work quite nicely.) Ultimately, since the blue light is a shorter wavelength (higher frequency), it is higher energy.
