21. A high-energy photon can collide with a free electron and give it some energy. (This is called the Compton effect.) How are the photon's energy, frequency, and wavelength affected by the collision?

23. An electron and a proton are moving with the same speed. Which has the longer de Broglie wavelength? (You may want to consult the Table of Conversion Factors for some useful information.)

25. What is the uncertainty principle?

27. What does it mean when a hydrogen atom is said to be in its "ground state"?

29. Describe the spectrum produced by ionized hydrogenthat is, a sample of hydrogen atoms all of which have lost one electron.

33. Radioactive strontium (Sr) tends to concentrate in the bones of people who ingest it. Why might one expect that strontium would behave like calcium (Ca) chemically and thus be preferentially bound in bone material, which is predominantly calcium in composition?

35. Will the frequency of the K peak in the x-ray spectrum of copper (Cu) be higher or lower than the frequency of the K peak of tungsten (W)? Explain how you arrived at your answer.

37. What is the origin of the word laser?

39. Distinguish between a metastable state and a normally allowed energy state within an atom. Discuss the role of metastable states in the operation of laser systems.

41. Describe the operation of a pulsed ruby laser.