2. Two conducting parallel plates, one 0.1m above the other, are held at an adjustable potential difference. An electrically negatively-charged drop of oil of mass 10-15 kg is found to fall at a constant speed when the plates are held at 2000 V. a. Which of the plates is positively charged? b. What is the charge on the drop? c. The voltage on the plates is now flipped, so that the field pushes the charge downwards. If the charge starts at rest, what is its velocity just before it hits the bottom plate if it falls the full 0.1m between the plates? 

5. There are a few problems in this part.

a. Light of wavelength 500nm is incident on a diffraction grating with spacing 2 x 10-6 m. The bright ray second from the center one will emerge at what angle from it?

b. Find the energy in Joules that is released when an electron and anti-electron (the antielectron has the same mass but opposite charge of the electron) collide and transform into energy.

c. Find the wavelength of the photon emitted when an electron in a hydrogen atom jumps from the n=3 to the n=1 state.