Physics Revision Questions

Question 1

What is EM radiation

Answer 1

The flow of energy created by simultanesoulsy varying the eletrical and magnetic fields

Question 2

Order of EM spectrum (longest wavelength, low freq and energy - shortest wavelength, high freq and energy)

Answer 2

Radiowave
Microwave
Infrared
Visible light
UV
Xray
Gamma ray

Question 3

Frequency

Answer 3

how many times the wave shape repeats per unit time

Question 4

Wavelength

Answer 4

distances over which the wave shape repeats itself

Question 5

Speed

Answer 5

freq x wavelength - energy directly porpotional to the freq

Question 6

1eV

Answer 6

Energy in joules gained by 1 electron moving across a potential difference of 1 volt

Question 7

Continous spectrum

Answer 7

incoming electron passes close to the nucleus of a target atom
electron rapdily declerated and deflected
amount of decleration and deflection proportioanl to electron loss
electron loss is in the form of EM radiation is a continous spectrum of energies

Question 8

Characterstic spectrum

Answer 8

incoming electron collides with inner shell target electron
Target electron displaced to an outer shell or completely lost from atom
Target atom unstable
Orbiting electrons rearranged to fill vacant orbital slots to return atom to natrual state
Difference in electron between orbits is released as charaterstic radiation known as electron values

Question 9

Attenuation

Answer 9

Reduction in number of xray photons within the beam

Question 10

How to reduce radiation scatter

Answer 10

Lead foil within the film packet which prevents back scattered photons from oral tissues reaching film
Fast films - F speed
Short exposure time
Rectuangual collomator tubes

Question 11

Recuce radiation dose to patient

Answer 11

Rectangualr collimator for intra oral radiographs
focus to skin distance @20cm 
F speed film
Use film holders and beam aiming device
Increase Kvp
Justification

Question 12

Photoelectric absorption, occurence proptional to

Answer 12

Atomic number (Z^3)
1/photon energy^3 (1Kv^3)
Densitiy of material

Question 13

Ways to decrease radiation does for staff?

Answer 13

No one other than patient go within 1.5mm of dental xray set and no where within primary beam while in operation
Do not hold image recpetor during exposure
Stand away from primary beam
Do not direct beam so it passes into adjacent room
Warning signs on doors
Lead apron for any person who has to be with patient
Film badge monitoring - >100 - PA/week or >40 OPTs/week