1. Describe the relationship between scatter and beam energy. Discuss how the different types of photon interactions govern this relationship.

2. You expose a patient phantom with x-rays and perform a preliminary measurement of the scatter onto the image receptor. The measurement that includes the transmitted beam and scatter yields 10,000 photons in 1 second. Covering off the scatter and measuring only the transmitted beam, you obtain 9,500 photons in 1 second. How large is the error of the scatter portion based on these measurements? You would like to increase your confidence in the scatter portion of the measurement and obtain this value with a precision of 3%. How long do you need to measure the beam with scatter and the beam without scatter, assuming that you will allocate equal measurement time for each?

3. Derivation of the equation you used to calculate the linear attenuation coefficient of the penny material. Be sure to clearly define your variables

4. U.S. Jefferson nickels produced today have a percent composition by weight of 75% copper and 25% nickel. However, during World War II, nickel was needed for production of military items. Therefore, from 1942-1945 nickels were minted that had the same mass as those today but with a percent composition by weight of 56% copper, 35% silver, and 9% manganese. If two nickels, one minted in 1945 and one minted in 1997, were radiographically imaged with an average beam energy of 70 keV and equal beam intensities, which nickel would yield the image with the higher optical density? Justify your answer.