Radiographic interpretation (10 Q&A)

Date 02-11-2010 12:41

need help to correct any wrong answers I have answer to these questions

21. Gamma radiation: MY ANSWER IS B
a. Is visible
b. ionizes matter
c. Has an odor
d. Is hot to the touch
e. Smells like acetylene gas or rotten eggs

22. Ionization refers to: MY ANSWER IS B
a. Slowing down of electrons production x-radiation
b. Any action that results in change in the electrical balance of the atom
c. Scatter
d. Photon or bundle of electromagnetic energy
e. How fast the electrons are moving

23. The general method of productin x-rays involves the sudden declaration of high velocity electrons in a solid body called a: MY ANSWER IS B
a. Focus cup
b. Filament
c. Cathode
d. Attinuator
e. Target

24. The velocity of electrons striking the target in an x-ray tube is a function of: MY ANSWER IS E
a. The atomic number of the cathode material
b. The atomic number of the filament material
c. the current flow in the rectifier circuit
d. The atomic weight of the photon striking the target
e. The voltage difference between the cathode and anode

25. A source of Iridium-192 whose half-life is 75 days, provides an optimum exposure of a given test object today in a period of twenty minutes. Five months from now, what exposure time would be required for the same radiographic density, under similar exposure conditions? MY ANSWER: DO NOT KNOW?
a. 10 minutes
b. 20 minutes
c. 1 hour and 20 minutes
d. 6 hours
e. none of the above

26. The gamma ray intensity at one foot from a one curie source of radioactive colbalt-60 is nearest: MY ANSWER IS A
a. 15 roentgens per hour
b. 1,000 roentgens per hour
c. 1 roentgens per minute
d. 10 milliroentgens per day
e. none of the above

27. The unit of measure of x or gamma radiation in air is the : MY ANSWER IS C
a. millicurie
b. gamma
c.roentgen
d. curie
e. milliampere

28. Which of the following is an advantage to the radiographer of using a gamma ray source rather than an x-ray machine? MY ANSWER IS B
a. Radiographs generally have less contrast, but greater latitude
b. Greater portability
c. Radiographs will generally have greater contrast, but less latitude
d. The ability to control radiation energy and intensity
e. the gamma ray sources are easily replaced.

29. When only a portion of a photon's energy is absorbed as it collides with an electron in an atom in the test specimen, the ionization process involved is called: MY ANSWER IS A
a. photoelectric effect
b. compton effect
c. pair production
d. partial ionization
e. photon transformation

30. The process whereby electrons are liberated from the x-ray tube's filament and the current applied to the filament is increased is called: MY ANSWER..I DON'T KNOW
a. Thermionic emission
b. Electron emission
c. Electron acceleration
d. Electron exication
e. None of the above

By ndeguy

Date 02-24-2010 07:10 Edited 02-24-2010 12:48

travishtn

Sorry for the delay but...

Q25 Half-life of Ir-192 is given as 75 days. 5 months is approximately 30 x 5 = 150 days or 2 Ir-192 half lives.

Required duration (Curie-minutes) at original exposure is 20 minutes. After one half-life curies have halfed so minutes must double to compensate. After 2 half-lifes Curies haves quartered so time must be quadrupled, i.e. 4 x 20 minutes = 80 minutes. ANSWER C.

Q23. Wrong, the current passed through the filament causes electron production through thermionic emission - this gives you the answer to question 30 also!. These electrons are accelerated from the anode towards the cathode through the electrical potential difference applied across the anode and cathode. These accelerated electrons impact on the target and are decelerated with the consequent production of X-rays. So in my book the answer is E. SOme may say C because the tungsten target is housed within the heat-dissipating cathode.