Hi!
This question is translated so that's why it might sound a bit weird. I know that the answer should mention the band diagram of the LED, and I think that the answer is to introduce an electrical contact connected to a voltage source. Then when you increase the voltage, it should attract the...
I calculated the answer for question a to be about 10^-6 m/s (1 significant figure), but I am stuck on question b. It seems to me that it is a trick question because we don't know anything about the speed in the y-direction, and the answer can be everything from 0 to infinity. Am I right?