EM Spectrum Flashcards
What is a wave?
- Waves transfer energy from one place to another without matter being transferred.
E.g. Mexican wave.
What is the substance that waves travel through?
Some waves need a substance to travel through - MEDIUM
Name the two types of waves
Mechanical - require a medium e.g. sound waves.
Electromagnetic - can travel in a vacuum e.g. X-rays.
What is the difference between a longitudinal and transverse wave?
Longitudinal
Oscillations – same direction as direction of travel and energy transfer. 0
e.g. sound waves.
Transverse
Oscillations – at right angles to direction of travel and energy transfer.
e.g. Electromagnetic waves are transverse. N
Oscillation - repeated motion.
What waves require a transportation medium to propagate from one point to another?
Mechanical waves
What waves can travel in a vacuum?
Electromagnetic waves which are transverse.
What is electromagnetic radiation?
- Electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry electromagnetic radiant energy.
- Transverse waves + travel in a vacuum
- Electromagnetic waves or radiation can be separated into seven
distinct groups in the spectrum. - These are: Radio waves, microwaves, infrared, (visible) light,
ultraviolet, X-rays, and gamma rays. - They are called the Electromagnetic Spectrum
What is the EM spectrum?
- EM is the range of wavelengths that forms the electromagnetic radiation.
- Different types of radiation occur in different parts of the EM spectrum.
Shorter wavelength to longer wavelength
S Gamma rays, X-ray, ultraviolet, visible, infrared, microwave and radio waves. L
List the properties of EM Radiation.
- Can all travel in a vacuum
- Are transverse waves
- Consists of oscillating electric (up and down) & magnetic fields (side to side).
- Propagates (to ‘move through’ or ‘transmit’) in straight lines
- Crucial in imaging
- Carries energy in a mass less form
- All travel at the speed of light in a vacuum
i.e. 3 x 108 m per sec (More accurately 2.999792458 x 108 m per sec) denoted by the symbol ‘C’ .
What is the amplitude of the EM waves?
Maximum electricity (or magnetic field) strength experienced at a particular point in space.
What is the wavelength of EM waves?
• Distance between two corresponding points on two successive waves.
What is frequency in regards to waves?
• The frequency of a wave is the number of waves produced by a source each second.
• It is also the number of waves that pass a certain point each second.
What is the unit of frequency?
• The unit of frequency is the hertz (Hz). It is common for kilohertz (kHz), megahertz (MHz) and gigahertz (GHz) to be used when waves have very high frequencies.
• For example, most people cannot hear a high-pitched sound above 20kHz, radio stations broadcast radio waves with frequencies of about 100MHz, while most wireless computer networks operate at 2.4GHz.
What is the equation for speed of EM radiation in a vacuum?
C = λ x v
c = constant speed/ Velocity (Speed of Light = 3 x 108 m/sec)
λ = wavelength (metre)
V = frequency (hertz)
wave speed (metre per second) = wavelength (metre) x frequency (hertz)
What is the equation of the energy of a photon?
E = h x v
E = Energy of a photon (joules)
h = Planck’s Constant (6.62 x 10-34 J sec )
V = frequency (hertz)
What are the units of measure used?
SI Unit Energy – Joule (J)
Alternative unit – Electron Volt (eV)
Relationship:
In physics, the electron volt is a unit of energy equal to approximately 1.6×10−19 Joule . By definition, it is the amount of energy gained by the charge of a single electron moved across an electric potential difference of one volt.
What is the effect of Frequency on EM energy?
EM radiation/wave energy is proportional to frequency.
EM radiation with high frequency has high energy. X-rays and gamma have high frequencies = Ionising
EM Radiation of lower frequencies (i.e., visible light, infrared, microwaves, and radio waves) is called non-ionising radiation
What are the effects of wavelength on EM energy?
EM radiation energy is inversely proportional to wavelength
I.e. Short wavelength = high energy EM radiation
E.g. X-rays and gamma radiation have short wavelengths.
Describe visible light.
Red has the lowest frequency + longest wavelength
Red, Orange, Yellow, Green, Blue, Indigo, Violet
Richard Of York Gave Battle In Vain
Violet has the highest frequency + shortest wavelength
Explain the relation between wavelength, frequency, and energy
EM Spectrum: decrease wavelength then frequency, and energy increases.
As wavelength decreases, frequency increases, and energy increases
What are radio waves used for?
• MRI uses radio waves (within a magnetic field) to create an image
• Also used to accelerate electrons in a linear accelerator
What are microwaves used for?
- Can be used for treating liver metastasis
- ‘Microwave ablation’ - treatment that uses heat from microwave energy to destroy cancer cells.
What are infrared waves used for?
- Used in breast imaging (thermography)
- Hotter areas / objects emit more infrared radiation
(emit shorter wavelength radiation)
What is visible light used for?
Endoscope e.g. in the duodenum
What is ultraviolet used for?
- Germicidal radiation
- treatment of skin conditions.
What are gamma rays used for?
- Radionuclide imaging (RNI)
- Sealed and unsealed source radiotherapy
Which modality does not use electromagnetic radiation?
Ultrasound
Which radiation can travel through a vacuum?
Radio waves
Microwaves
Infrared
visible light
X-rays
Gamma rays
Are waves on the electromagnetic spectrum, transverse or longitudinal?
Transverse
What is meant by a transverse wave?
A wave where oscillations occur at right angles to the direction of travel and energy transfer.
What field do transverse waves have?
Both an oscillating electric and magnetic field
Rank the visible lights in order of frequency (lowest frequency at the top, highest frequency at the bottom)
Red, Orange, Yellow, Green, Blue, Indigo, Violet
Rank the visible lights in order of wavelength (longest wavelength at the top, shortest wavelength at the bottom)
Red
Orange,
Yellow,
Green,
Blue,
Indigo,
Violet
Rank the EM radiations in order of frequency. (Highest frequency at the top, lowest frequency at the bottom)
Gamma rays
X-rays
Ultraviolet
Visible light
Infrared
Microwaves
Radio waves
Name the 7 different visible lights
Red, orange, yellow, green, blue, indigo, violet
Rank the EM radiations in order of energy. (Highest energy at the top, lowest energy at the bottom)
Gamma rays
X-rays
Ultraviolet
Visible
Infrared
Microwaves
Radio waves
Which EM radiation has the highest frequency and the shortest wavelength? Ultraviolet or visible light?
Ultraviolet
Which has the lowest frequency and the longest wavelength?
Gamma rays, microwaves or Ultraviolet?
Microwaves
What is the energy of a photon?
Planck’s constant multiplied by the frequency
What is the SI unit of energy?
Joule (J)
What is the unit of frequency?
Hertz
What uses Radio waves?
MRI
What does half-life (T1/2) describe ?
The amount of time needed for half of a sample of unstable atoms or particles to undergo decay.
What are the types of radioactivity decay?
Alpha
Gamma
Beta
What is alpha decay?
Alpha decay is the emission of 2 protons and 2 neutrons from an unstable neutrons. The daughter nuclide has an atomic number of 2 less than the parent nuclide.
