Medical Physics Flashcards
OCR Physics A - Unit 6 (Medical Physics)
1
Q
What is the function of Cathode in an X-Ray tube?
A
- To produce electrons, through thermionic emission.
2
Q
What is thermionic emission?
A
- The release of electrons from a surface due to thermal energy.
3
Q
How are X-Ray photons produced at the anode?
A
- The electrons from the Cathode are attracted to the Anode.
- The electrons are decelerated.
4
Q
What is the function of a Target metal in an X-Ray Photo tube?
A
- Has a high melting point.
- Some of the energy from the electrons is transferred to thermal energy.
- A high melting point reduces chance of melting inside the tube during X-Rays.
5
Q
What is the function of the high voltage power supply across the tube?
A
- To create a large potential difference between the two electrodes.
6
Q
Why is the tube an evacuated chamber?
A
- To prevent interference between air and the electrons, meaning the maximum number arrive at the anode.
7
Q
Why would increasing the current in an X-ray tube increase the beam intensity?
A
- The current is the rate of flow of charge carriers (E.G electrons).
- An increased current means an increased number of electrons leaving the Cathode.
- More electrons leaving the cathode means more converted into photons at the anode.
8
Q
State the typical range of wavelengths for X-Rays.
A
- x10^16 - x10^19 Hz.
