19. Light hits a double slit before hitting a screen. (a) the image will be a line (b) the image will be several lines (c) the image will be two lines (d) there will be no image. 20. Bohr's model (a) succeeds only for hydrogen (b) succeeds for helium (c) results in spiraling electrons (d) predicts the electron spin. 21. Heisenberg's uncertainty principle is (a) strictly quantum (b) strictly classical (c) does not violate determinism (d) none of the above. 22. In free space the speed of light (a) is constant (b) depends on the source (c) depends on the observer (d) none of the above. 23. Bohr's atomic model has (a) one quantum number (b) two quantum numbers (c) three quantum numbers (d) four quantum numbers. 24. Blackbody radiation is explained by (a) classical electromagnetic waves (b) quantization of light (c) photo electric effect (d) Wien's law. 25. The photoelectric effect (a) won Einstein a Nobel prize (b) may be explained by classical theory (c) is not dependent on the work function (d) none of the above. to a lower orbit