waves, electromagnetism and properties of X-Rays

Question 1

what are x-rays?

Answer 1

a form of electromagnetic radiation, x-ray photons are a form of ionising radiation

Question 2

wavelength

Answer 2

distance measured between two successive points on a wave

Question 3

frequency

Answer 3

number of oscillations that pass through a given point in a specified period of time (usually one second)

Question 4

intensity

Answer 4

power transferred per unit area, where the area is measured on the plane perpendicular to the direction of the propagation of energy

Question 5

inverse square law

Answer 5

intensity=1/x2

• applies when the wave travels outward from a point source
• intensity falls as a constant energy becomes spread over a larger area
• at 2x the distance from the source, intensity is 0.25 of the previous value
• double distance= quarter intensity

Question 6

Electromagnetic Radiation properties

Answer 6

• do not require a medium for propagation
• transmitted by combined electrical and magnetic fields
• travel at the speed of light in a vacuum
• may interact with matter and be absorbed or scatttered

Question 7

What are the properties of X-Rays

Answer 7

• fluorescence (cause some substances to emit visible light after absorbing x-rays)
• photographic effect
• penetration (penetrate substances that are opaque to visible light)
• Biological effect (cause changes to tissue)

Question 8

When are X-Rays produced?

Answer 8

when fast moving electrons are slowed down in passing through matter. beams of x-rays are not mono- energetic, they contain a range of energies in a continuous spectrum

Question 9

Electron-Volt (eV)

Answer 9

kinetic energy gained by an electron from being accelerated across a potential difference of 1 volt in a vacuum.

Question 10

x-ray spectrum

Answer 10

• the spectrum has a maximum photon energy equal to the tube voltage when the energy is expressed in electron volts
• photons of maximum energy have the maximum wavelength within the spectrum
• kVp is the peak tube voltage

Question 11

what happens when you increase the tube voltage

Answer 11

• an increase in the tube voltage increases the intensity of emission of all photon energies
• increasing the voltage increases the proportion of high energy photons.
• higher energy photons have greater penetrating power so increasing the tube voltage increases the penetrating power of the beam