Electromagnetic Radiation

Question 1

On the electromagnetic spectrum describe which direction it increases in frequency and which direction increases in wavelength

Answer 1

from right to left has increasing frequency (Hz)

from left to right has increasing wavelengths (lamda)

Question 2

Describe properties of all types of electromagnetic radiation - 7 points

Answer 2

carry energy, travel at 3 x 10 to the power 8 ms to the -1 (speed of light ‘c’), can travel in a vacuum (sound needs a vacuum), their intensity obeys the Inverse Square Law, unaffected by electric and magnetic fields, travel in straight lines, have frequency, wavelength and amplitude

Question 3

Describe ionising radiations

Answer 3

some types of wave (e.g. x-ray/gamma rays) can ionise atoms, can be harmful

Question 4

Describe non-ionising radiations

Answer 4

other types of wave (e.g. infra-red and radio) cannot ionise matter

Question 5

Name the 2 models of electromagnetic radiation

Answer 5

The wave model, the proton model

Question 6

The electromagnetic wave is composed of …

Answer 6

sinusoidally alternating electric and magnetic fields

Question 7

Define wavelength (lambda)

Answer 7

the distance between corresponding points on 2 consecutive cycles

Question 8

Define frequency (f)

Answer 8

number of complete cycles occurring p/s - Hz

Question 9

Define period (T)

Answer 9

time taken for the wave to complete 1 cycle, T = 1/f

Question 10

V = f(lambda)

Answer 10

Velocity = frequency x wavelength

Question 11

Define amplitude

Answer 11

the “vigour” of the wave

Question 12

Define cycle

Answer 12

One complete oscillation of the wave

Question 13

Quanta/Photons

Answer 13

a more appropriate term for electromagnetic radiation, a stream of discrete ‘packets’ of energy

Question 14

Equation for the amount of energy photons have carried

Answer 14

E = h x f, E = photon energy (J), h = Planck’s constant (6.626 x 10 to the power of -34 J.S), f = frequency of radiation (Hz)

a substitute for f = c/(lambda)

Question 15

‘Wave particle duality’

Answer 15

the wave theory and the photon theory existing simultaneously - each can be used to explain different phenomena (interference - best explained using wave theory, x-ray production/absorption - best explained using photon theory)

Question 16

Define spectrum

Answer 16

a spectrum is a graph which shows the energy distribution of the radiation present, whatever its type

Question 17

Define Intensity

Answer 17

amount of energy flowing per unit area, per unit time, measured along a plane at 90 degrees to the direction of travel of the radiation
J.m^-2.s^-1 Joules per metre squared per second

Question 18

Describe the inverse square law

Answer 18

intensity of radiation from a point source varies inversely with the square of the distance from the source provided there’s no attenuation by the medium through which the beam is travelling
Intensity is proportional to 1 over the distance squared
I a 1/d squared

Question 19

As the distance from the source of radiation gets greater, the intensity of that radiation …

Answer 19

get smaller

Question 20

The inverse square law is significant in practice when …

Answer 20

calculating exposure factors, radiation protection requirements, radiation dose

Question 21

I1 x (d1) squared = I2 x (d2) sqaured 
^^ write this out in words

Answer 21

Intensity at the original distance times the original distance squared equals the intensity at the new distance times the new distance squared

Question 22

X-Rays are measured in

Answer 22

keV

Question 23

Define stochastic

Answer 23

random (cancer odds)

Question 24

Define deterministic

Answer 24

known threshold (hairloss)

Question 25

Define somatic

Answer 25

happens to patients through radiation

Question 26

Define genetic

Answer 26

passes onto offspring - radiated parent

Question 27

Which 4 places do X-Rays originate from

Answer 27

outer space/radioisotopes/X-Ray tubes/linear accelerators