Electromagnetic Spectrum Flashcards
What is electromagnetic radiation?
Electromagnetic (EM) Radiation is a form of energy and means of energy transfer. The wavelength determines position and wave frequency on the electromagnetic spectrum.
The most obvious for of EM radiation is light.
List the types of EM radiation from the longest to shortest wavelengths?
Radio, Micro, Infa-red, Light, Ultraviolet, Xray, Gamma
What is the relationship between wavelength and frequency?
The longer the wavelength the lower the frequency and vice versa
What is wave/particle duality?
Wave/particle duality is the concept that EM radiation exists as 2 different conceptual forms. As a wave and as a particle.
At longer wavelengths (lower frequencies) the energy behaves more like a wave, at shorter wavelengths (higher frequencies) it behaves more like a particle.
For example, light exhibits properties of particles known as photons/quanta. It also behaves as a wave where light will diffract and reflect.
What happens to EM radiation in a vacuum?
It will propagate at a constant rate (the speed of light)
What is the shape of the waveform in EM radiation?
it is sinusoidal
How is frequency of a waveform defined?
The frequency of the wave is defined as:
The number of wavelengths passing a fixed point in one second, or the number of cycles per second given in Hertz (Hz).
Write a formula which links wavelength, frequency and speed of travel?
λ x ν = c
λ = wavelength
ν = frequency
c = speed constant (speed of light)
What are the different types of wave transmission?
Wave transmission occurs as oscillating sine waves.
They can be:
+ Longitudinal
+ Transverse
Longitudinal waves oscillate parallel to the direction of travel (e.g. sound)
Transverse waves oscillate at a right angle to the direction of travel.
What sort of wave transmission does EM radiation exhibit?
EM radiation travels as a transverse sine wave.
It consists of 2 distinct oscillations perpendicular to the direction of travel of the wave:
One is an electrical field and the other is a magnetic field which also oscillate at right angles to each other and to direction of travel.
(If direction of travel is the x axis, one field would be the y axis and the other would be the z axis)
What is the relationship between frequency and energy transmission in Electromagnetic waves?
The higher the frequency the more energy that is emitted (gamma rays have the highest frequency and emit the most energy and are therefore the most harmful)
The relationship can be demonstrated in the following formula.
E= v x h
E= energy
v = frequency
h= planks constant
Explain the principle underpinning a laser?
As previously mentioned EM radiation exhibits wave/particle duality.
We must consider its particle characteristics.
Atoms are surrounded nuclei surrounded by electron orbitals, and electrons are in different level orbitals.
If an atom absorbs energy an electron will move energy level to a higher energy level orbital, as it drops back down to a lower energy level orbital it will emit energy in the form of a photon.
The amount of energy between orbitals is known as the quantum. Each atom has a different value quantum.
As previously stated energy is directly related to frequency and frequency is directly related to wavelength. Therefore each photon which is emitted has a specific wavelength which varies depending on the atom.
Laser stands for Light Amplification by Stimulated Emission of Radiation.
It uses the above principle by using a high energy source to stimulate a lasing medium (often CO2 or Argon) which takes up the energy and as the electrons drop back to a lower energy orbital emit a photon.
How does absorption spectroscopy work?
Consider a gas that is stimulated by an energy source, such as infrared radiation or visible light.
If the gas contains two or more different atoms in its molecules, specific amounts of energy are absorbed by a change in the conformation of the energy state of the electrons in the different atoms in the molecule.
As seen already, specific amounts of energy relate to specific wavelengths in EM radiation.
If a sensor looks at the radiation that has passed through this gas, the absorbed energy shows as ‘missing’ spectral lines, i.e. missing wavelengths, detected by the sensor.
How does Infared gas analysers work?
Infrared Gas Analyzers makes use of absorption spectroscopy on the infrared region of the EM spectrum.
The amount of infrared energy absorbed at each specific wavelength (according to type of gas present) depends on the amount of each gas present.
Therefore, it is able to detect the type and concentration of gases present by comparing with a reference chamber of known gases and their concentration.
Only molecules with pairs of atoms of different elements absorb infrared radiation. This is why oxygen is not measured by the infrared gas analyzer.
