Physics Basics Flashcards
What speed does light travel at?
3x108 ms-1
What is frequency measured in? And what is it?
Measured in Hertz, Hz
Frequency is how many times the wave’s shape repeats per unit time
What is wavelength measured in? And what is it?
Measured in Metres, M
The distance over which the wave’s shape repeats
What is the Basic Production of X-rays?
Electrons fired at atoms at very high speed
On collision, the kinetic energy of these electrons is coverted to electromagnetic radiation (ideally X-rays) & heat
The X-rays photons are aimed at subject
What does the Atomic Number of an atom tell you?
The number of protons in an atom
What does the Mass Number of an atom tell you?
The number of protons and neutrons in the nucleus
How are orbiting electrons held within their shells?
How do you remove an electron from its shell?
Electrostatic Force (the innermost shells are highest energy)
Removal of electron from its shell is by binding energy
What is the Tubehead?
Box within casing where the X-rays are created
What direction do X-rays require? What process does this?
Unidirectional
As they are powered by mains, rectification process occurs. X-rays have generators which modify the alternating current so that it mimics a constant direct current
What is the purpose of a transformer?
Why is this needed?
What are the 2 separate ones required for an X-ray unit?
Alter the voltage from 1 circuit to another
As X-rays require 2 different voltages (one really high, one really low)
Mains - X-ray tube (cathode-anode)
Mains- Filament
(step-up transformer and step-down transformer)
How do photons travel from the X-ray source?
They diverge (i.e. dose decreased with distance from X-ray source)
What is the Inverse Square Law?
Intensity of X-ray beam is inversely proportional to the square of the distance between the X-ray source and the point of measurement
Doubling the distance will quarter the dose
