EM Radiation | Bright Minds Mentori

EM radiation is a form of energy which has a

dual nature; acting both as a wave or a particle.

aka wave-particle duality

.

Bands of energy which have their own specific frequency & wavelength.

Frequency & wavelength are inversely proportional.

1. frequency (f)

Number of waves that pass a fixed

point in 1 second. (Hz/S1)

2 wavelength (λ)

Distance between two crests/troughs

(nm = 10 )

3. wave number

number of waves in 1m OR 1cm

1/wavelength

Unit = m OR cm

Different types of radiation arranged in order of increasing frequency/decreasing wavelength.

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When EM radiation is absorbed/transmitted by matter, it acts as a stream of particles called photons which can transfer small bundles (packets) of energy.

A photon carries quantised energy proportional to the frequency of radiation.

Higher Frequency radiation Lower Frequency radiation

Transfer greater levels of energy Transfer lower levels of energy

The energy released/absorbed by 1 mole of photons (kJ mol) can be calculated using the equations below.

Example calculation 1 - wavelength to calculate energy

Example calculation 2 - energy to calculate wavelength (rearrange)

Example calculation 3 - frequency to calculate energy

Photon absorbed by matter

Electrons gains energy, becoming

excited & promoted to a higher

energy level.

Photon emitted by matter

Energy is lost by electrons as electrons

move from a higher to lower energy

level.

A series of lines are created as photons are absorbed/emitted from atoms as electrons transition between one energy level & another.

Spectroscopy is used to test the following in a sample by either measuring absorption/emission.

1. Types of Elements present

Each element has a characteristic absorption/emission spectrum

2. Concentration of each element

The concentration of an element within a sample is related to the intensity of light emitted or absorbed.

Measures the concentration of an element in sample by intensity of absorbed light at different wavelengths of EM radiation.

EM radiation is directed at an atomised sample &

radiation is absorbed as electrons are promoted

to higher energy levels.

Measures the concentration of an element by intensity of light emitted at different wavelengths.

High temperatures are used to excite the

electrons within atoms.

As the electrons drop to lower energy levels,

photons are emitted producing

Colour of line

1. 400 to 700nm emitted = colour of sample

2. 300nm emitted = UV colourless sample

Emitted wavelength = coloured line

Absorbed wavelength = black line