eLFH - Electromagnetic spectrum

Question 1

Electromagnetic radiation definition

Answer 1

Form of energy and means of energy transfer

Spectrum - includes visible light

Question 2

Composition of electromagnetic radiation

Answer 2

Electrical wave and magnetic wave
Both are perpendicular to each other and the direction of travel

Question 3

Electromagnetic spectrum definition

Answer 3

Different types of electromagnetic radiation with varying wavelengths

Question 4

Electromagnetic spectrum

Answer 4

Question 5

Wave or Particle duality definition

Answer 5

Electromagnetic radiation can exhibit properties of both particles (with packets of energy e.g. photons) and waves (e.g. diffraction and reflection)

Longer wavelengths show more wave properties, and shorter wavelengths show more particle properties

Question 6

How is electromagnetic radiation generated

Answer 6

Oscillation of charged particles and their electrical field lines - mainly protons +/- electrons

Question 7

Speed of EM radiation in a vacuum

Answer 7

Speed of light
= 2.98 x10^8 m/s

Question 8

Frequency definition

Answer 8

Number of wavelengths passing a fixed point per second in Hertz

Question 9

Wavelength definition

Answer 9

Distance from one peak of the sine wave to the next

Question 10

Relationship between wavelength and frequency

Answer 10

Lambda = wavelength
Nu (v) = frequency
c = speed of light, constant

Therefore wavelength and frequency are inversely proportional, hence why frequency increases and wavelength decreases

Question 11

Types of oscillating sine waves

Answer 11

Longitudinal

Transverse

Question 12

Longitudinal waves

Answer 12

Direction of oscillation is parallel to direction of travel of waveform

E.g. sound - propagates by compression of air molecules

Question 13

Transverse waves

Answer 13

Direction of oscillation is perpendicular to direction of travel of waveform

EM radiation is a transverse wave

Question 14

Quanta definition

Answer 14

Discrete packets of energy carried by electromagnetic waves

Also referred to as photons

Question 15

Relationship between energy and frequency

Answer 15

E = h x v

E = energy
v = frequency
h = Planck’s constant

Higher frequency waves have higher energy

Question 16

Quantum energy levels

Answer 16

When an atom is stimulated by external energy, electrons move up to higher energy orbitals

As they move down to lower energy orbital / back to ground state, photon / EM radiation is emitted

Different atoms / elements emit different wavelength of EM radiation across the spectrum

Question 17

Absorption spectroscopy

Answer 17

Energy absorbed by a gas when energy source passed through it can be used to help identify the substance / gas through which it passed

Specific wavelengths of EM radiation will be absorbed and therefore will not be detected by sensor on the other side

Question 18

Infrared gas analyser

Answer 18

Uses absorption spectroscopy with infrared light to identify gases in a mixture and their concentrations by measuring absorbed wavelengths by the test sample and comparing this to a reference chamber of fixed composition

Works because precise wavelengths absorbed by different gases varies

Question 19

Requirements of a gas to be detected by infrared gas analyser

Answer 19

Gas must be composed of pairs of atoms of different elements

Otherwise they don’t absorb infrared radiation

E.g. CO2, N2O and volatile agents can be measured, but O2 cannot be measured by infrared gas analyser