Electromagnetic Spectrum + Particle Radiation PDF

Electromagnetic Spectrum + Particle Radiation HS1934 – Introduction to Radiography Winnie Tam Electromagnetic Spectrum + Particle Radiation Learning Outcomes This lecture will cover the following topics stated in the HS1934 Learning outcomes HS1934 Content outline:...

Electromagnetic Spectrum + Particle Radiation HS1934 – Introduction to Radiography Winnie Tam Electromagnetic Spectrum + Particle Radiation Learning Outcomes This lecture will cover the following topics stated in the HS1934 Learning outcomes HS1934 Content outline: Knowledge Describe the fundamental principles of radiation physics Radiation physics principles underpinning radiographic relevant to the operation and function of diagnostic practice including: imaging and therapeutic radiography equipment. Atomic structure Outline the basic radiobiological principles that underpin Electromagnetic spectrum radiographic practice. Discuss the fundamental principles of safe practice X-ray production and interaction with matter concerning radiation protection and legislation. Radioactivity Skills Demonstrate the application of basic radiation physics Principles of diagnostic and therapeutic radiography principles. practice including: Demonstrate effective communication skills using medical Patient pathway in diagnostic and therapeutic terminology related to radiography. radiography Describe the role of radiographers in the interprofessional Introduction to diagnostic imaging modalities team. Introduction to therapeutic treatment and imaging Reflect on your personal and professional development. modalities Values and attitudes: Outline the importance of good professional behaviour Radiation protection and legislation through your approach to your studies both in individual Professionalism and Service User experience and group settings. Electromagnetic Waves? Until the 19th Century, electricity and magnetism were considered separately. In 1820, a Danish scientist Hans Christian Oersted attempted to show his students at the University of Copenhagen that an electrical current of moving charges had nothing to do with magnetism. Oersted placed a segment of conducting wire close to and parallel with the usual north–south orientation of a compass needle. In actual fact, Oersted had unintentionally demonstrated that moving charges do produce a magnetic influence. Oersted Experiment https://www.youtube.com/watch?v=UmZuEMFagXA Electromagnetic Waves? Using Oersted and Faraday’s discoveries, James Clerk Maxwell formulated of a set of equations (Maxwell's equations), which describe electric and magnetic fields propagate perpendicularly (i.e. two fields interlock at 90° right angled to each other). These transverse waves are created when electric and magnetic fields interact and move together. Electromagnetic waves special is because no medium is needed (like air or water) to travel through, they can move through the vacuum of space. Visible light – the light we see covers a very small range of frequencies (or wavelengths) in the electromagnetic spectrum. Electromagnetic Spectrum? There are a range of values in the electromagnetic spectrum. Think about the colours of a rainbow à there are a range of colours The colours of a rainbow is only one tiny part of the whole electromagnetic spectrum. The speed of light and all waves in the EM spectrum is 𝟑×𝟏𝟎𝟖 𝐦/𝐬, although some particular waves have their own specific speed (e.g. speed of sound (in air) is 340 m/s). Comparison of different types of light, incl. wavelength size, & frequency  Anatomy of a Wave Wavelength (λ (lambda)) The distance between one peak and the peak of the next wave. Frequency (f) The number of waves that pass a certain point each second. Amplitude (A) The maximum disturbance from its undisturbed position, not the distance between the top and bottom of a wave. Velocity (v) Wave speed, is a measure of how fast the wave moves through a medium (like air, water, or a vacuum). i.e.: how quickly the wave is traveling from one place to another. Velocity is speed with direction. Imagine you're holding one end of a rope, and you give it a quick flick. You’ll see a wave move along the rope from your hand to the other end. – The speed of this wave travels down the rope is its velocity.  Wave Equation frequency (unit: hertz, Hz) wavelength (unit: metres, m) wave speed v = f × λ (unit: metres per second, m/s) Calculate the speed of ultraviolet radiation. v=? v=f×λ f = 1.5 × 1015 Hz v = 1.5 × 1015 × 200 × 10-9 λ = 200 × 10-9 m v = 3 × 108 m/s. Time Period (T) Time Period is the time it takes for a wave to complete one cycle (i.e. one wavelength) Unit: seconds Think of being on a swing. Each swing back and forth, we can think of it like a wave: The swing starts at one point, moves forward, then swings back to its starting position. The time period is the time it takes for the swing to go from its starting point, move forward, come back, and return to the starting position. Wave Equation ! Time period T = " (unit: second) frequency (unit: hertz, Hz) A radio wave has a frequency of 3 MHz. What is its period? " f = 3 MHz = 3 ×10! Hz T= # " T= $ ×"'! T = 0.00000033 s (or 0.33 ×10(! s) A boat at sea bobs up and down as waves pass. The vertical distance between a crest and a trough is 52 cm, and 20 waves pass the boat in 30 seconds. 1. What is the amplitude of the waves? 2. What is the frequency of the waves? 1) The amplitude of a wave is the maximum 2) Frequency = number of waves to pass a point ÷ displacement of a point of a wave from its time taken in seconds rest position. number of waves = 20 This is exactly half the distance between a time taken = 30 s crest and trough. – The distance between a crest and – f = 20 ÷ 30 trough = 52 cm. – f = 0.67 Hz – amplitude = 52 cm ÷ 2 = 26 cm. – The frequency of the waves is 0.67 Hz. EM - Energy Relationship The energy of an electromagnetic wave is closely related to its frequency and wavelength. higher frequency waves carry more energy, This is why X-rays can pass through your body, and gamma rays are used in cancer treatment. while lower frequency waves carry less energy. Radio waves, for example, are used to transmit signals over long distances without causing harm. Considering the above, how does wavelength impact on the energy that the wave carries? Energy & Frequency The energy (E) of an electromagnetic wave is directly proportional to its frequency (f). Planck Constant: 6.626×10−34 joule-seconds Energy of the wave 𝐸 = ℎ ×𝑓 Unit: Joules (J) frequency (unit: hertz, Hz) Green light wave has a frequency of 540 THz. Calculate the energy of the green light wave. 𝐸 = ℎ ×𝑓 Planck Constant frequency E = 6.626×10−34 ×5.4 ×10") E = 3.58 ×10("* 𝐽 Energy & Wavelength Relationship between frequency and wavelength are inversely related (i.e.: higher frequency means shorter wavelength, and vice versa), The energy of the wave is also inversely related to wavelength (λ).  Planck Constant: Energy & Wavelength 6.626×10−34 joule-seconds Energy of the wave ℎ ×𝑐 speed of light in a vacuum (3×108 per second) 𝐸= Unit: Joules (J) 𝜆 A light has a wavelength of 500nm. What is the energy of this wave? wavelength (unit: metres, m) 500nm = 500×10−9 m = 5×10−7 m (6.626×10($) J⋅s)×(3×10+ m/s) E= 5× 10(, E = 3.98×10−19 J Everyday Applications of Radiation Radio The Italian scientist Guglielmo Marconi was the first to provide the practical implementation of radio waves. He created the first radio for which he was awarded the Nobel Prize in 1909. These waves were first used for commercial purposes in the 1900s. – Short radio waves: telecommunication. – Low-medium frequency radio waves: can easily travel underwater, and can penetrate the rocks, and are used in submarines, mining and geothermal activities. – Higher frequency radio waves: public radio services, and GPS. These waves transfer the information with the least disturbance and are used to send communication signals. Microwave Intense sources of microwaves can be dangerous through internal heating of body cells. Higher frequency microwaves have frequencies which are easily absorbed by molecules in food. The internal energy of the molecules increases when they absorb microwaves, which causes heating. Microwaves pass easily through haze, light rain and snow, clouds, and smoke. They are beneficial for satellite communication and studying the Earth from space. Infrared In 1800, William Herschel conducted an experiment measuring the difference in temperature between the colours in the visible spectrum. He noticed an even warmer temperature measurement just beyond the red end of the visible spectrum, and had discovered infrared light! We can sense some infrared energy as heat. Some objects are so hot they also emit visible light (e.g. fire). Other objects, such as humans, are not as hot and only emit only infrared waves. Planets, cool stars, nebulae, and many more, can be studied by the infrared waves they emit. Many objects in the universe are too cool and faint to be detected in visible light but can be detected by infrared. Visible Light All electromagnetic radiation is light, but we can only see a small portion of this radiation (i.e.: visible light). The light we can see, so is used in photography and illumination. It is also used in fibre optic communications, where coded pulses of light travel through glass fibres from a source to a receiver. As the full spectrum of visible light travels through a prism, the wavelengths separate into the colours of the rainbow because each colour is a different wavelength. Ultraviolet UV radiation is widely used in industrial processes and in medical and dental practices for a variety of purposes, such as killing bacteria, creating fluorescent effects, phototherapy and suntanning. Different UV wavelengths and intensities are used for different purposes. We cannot see ultraviolet (UV) light, but it can have hazardous effects on the human body. Though this also means UV will kill bacteria and can be used to disinfect water. Ultraviolet light in sunlight can cause the skin to tan or burn. UV light is used on bank notes to detect forgeries. X-Rays On November 8, 1895, while experimenting with a beam of electrons created within an evacuated glass tube, Wilhelm Conrad Röntgen (1845–1923) accidentally discovered certain “rays” that propagated beyond the end of his tube. These rays seemed to travel in straight lines, made florescent materials glow, and exposed photographic plates. The rays travelled through flesh but not through bone, because X-Rays transmit through body tissues and are only absorbed by dense structures like bones, which is why X-ray photos are used to help identify broken bones. Since Earth's atmosphere blocks X-Ray radiation, telescopes with x-ray detectors must be positioned above Earth's absorbing atmosphere. X-Ray can also be used to detect forgeries in art and antiquities. X-Ray usage in Astronomy The supernova remnant Cassiopeia A (Cas A) was imaged by three of NASA's observatories, and data from all three observatories were used to create the image. Infrared data from the Spitzer Space Telescope are coloured red, Optical data from the Hubble Space Telescope are yellow, and X-ray data from the Chandra X-ray Observatory are green and blue. Gamma Rays Gamma rays have the smallest wavelengths and the most energy of any wave in the electromagnetic spectrum. On Earth, gamma waves are generated by nuclear explosions, lightning, and radioactive decay. Unlike optical light and x-rays, gamma rays cannot be captured and reflected by mirrors. Gamma- ray wavelengths are so short that they can pass through the space within the atoms of a detector, and because of the short wavelength, Gamma rays can do body damage even when located outside of the body due to their penetrating power. The high energy can be used to – kill cancer cells, and – bacteria on food. – as a medical tracer by injecting the tracer into the body. An image is then formed when the gamma rays travel out of the body and are detected by a gamma camera. – Detect compositions of other planets Ionising Radiation (electromagnetic radiation) Ultraviolet waves, X-rays and gamma rays are types of ionising radiation. Ionising radiation can add or remove electrons from molecules, producing electrically charged ions, and have hazardous effects on the body: Ultraviolet waves can cause damage to skin cells and eyes, and increase the risk of skin cancer X-rays and gamma rays can cause the mutation of genes, which can lead to cancer. break The Double-Slit Experiment In 1803, Thomas Young demonstrated an experiment at the Royal Society of London. In a simple, modern form, Young’s ‘double-slit’ experiment involves shining light of a single frequency (e.g. a red laser) through two fine, parallel openings in a sheet, onto a screen beyond. The light passing through the double slits by diffraction, the two sets of waves overlap near the centre of the pattern (interference pattern) until it reaches the screen Interference is possible only if light behaves as a wave and diffracts through each slit, The intensity alternates from high to low, showing creating two sets of waves on the other side of interference in the signal from the two slits. the slits that propagate towards the screen. Bach R, Pope D, Liou SH, Batelaan H. Controlled double-slit electron diffraction. New Journal of Physics. 2013 Mar 13;15(3):033018. A Slap to Newton? Newton had, early in his career, explored the possibility that light was composed of waves. But the waves of which Newton was aware (sound and water waves) tend to bend (diffract), around barriers, while light, it seems, does not. (we can hear but not see around corners). Consequently, Newton was drawn to the idea of particles of light. However, if light were made of streams of particles, as Newton suggested: there should be two distinct strips of light on the screen, where the particles pile up after travelling through one slit or the other. And the interference pattern disproved Newton’s theory. Particle Theory Newton proposed that light consists of small, discrete particles, in which they are now known as photons. A photon is an elementary particle, each with a small bundle of quantised packets of energy, travelling through space at the speed of light. Electromagnetic radiation consists photons. A photon – is the smallest quantity of ANY type of electromagnetic radiation – has no mass, no electric charge. Photon energy and frequency are directly proportional. Single Particle Detection of the Double-Slit Experiment Firing a Slit photons If a single photon is being fired one by one single partition photons photon one through the double-slit with a low intensity: by one Single particles being detected as white dots on the screen. However, an interference pattern emerges when these particles are allowed to build up one by one. Pattern being built up dot-by-dot. Bach R, Pope D, Liou SH, Batelaan H. Controlled double-slit electron diffraction. New Journal of Physics. 2013 Mar 13;15(3):033018.  Wave-Particle Duality Photoelectric Effect This demonstrates the wave-particle duality, which explains that light exhibits both wave Compton Scattering Particles and particle properties: Single-Particle Version of the Double-Slit Experiment The particle is measured as a single pulse at a single position, while the pattern on the screen comes from the The Original Young’s Double-Slit Experiment chance of finding the particle in different Reflection Waves places, which creates a statistical interference pattern. Refraction  Photons from different regions of the spectrum are fundamentally the same. However, their difference in frequency results in differences in the way the photons interact with matter: – Visible photons behave more like waves – X-ray photons act more like particles break Types of Ionising Radiation Electromagnetic radiation (the one mentioned previously, In the previous slide, we learnt about ionising radiation. involves photons), and In fact, there are two types of ionising radiation: Particulate radiation Particulate Radiation Many sub-atomic particles are capable of causing ionisation, if: – They are in motion, and – Have enough kinetic energy At rest, they cannot cause ionisation. There were two main types of particulate radiation: – Alpha (α) particle – Beta (β) particle Atomic Structure: Recap Atoms are the smallest particles of an element that can exist without losing the chemical properties of the element. There are multiple models and theories to explain atomic structures and compositions, but the simple model suggested by Bohr is still the most common model and suffices most of the phenomena in medical physics.  The nucleus is formed by: – protons (positive charged) and – neutrons (no charge) Electrons are located outside the nucleus and have negative charges. Alpha (α) Decay When a nucleus has a mass > 150, and has too many protons and not enough neutrons Unstable Loses an α particle – a helium nucleus with two positive charges (protons x2, neutrons x2) Alpha (α) Decay When a nucleus has a mass > 150, and has too many protons and not enough neutrons Unstable Loses an α particle – a helium nucleus with two positive charges (protons x2, neutrons x2) Alpha (α) Decay When a nucleus has a mass > 150, and has too many protons and not enough neutrons Unstable Loses an α particle – a helium nucleus with two positive charges (protons x2, neutrons x2) Alpha (α) Decay When a nucleus has a mass > 150, and has too many protons and not enough neutrons Unstable Loses an α particle – a helium nucleus with two positive charges (protons x2, neutrons x2) 231 235 90 Th 92 U Alpha (α) Decay 4 α++ 2 (Helium nucleus) Beta Minus (β-) Decay When a nucleus has too many neutrons A neutron converts into a proton inside the nucleus. Emits a: β- particle (negative charged), and Anti-neutrino Beta Minus (β-) Decay When a nucleus has too many neutrons A neutron converts into a proton inside the nucleus. Emits a: β- particle (negative charged), and Anti-neutrino Beta Minus (β-) Decay When a nucleus has too many neutrons 14 A neutron converts into a proton inside the nucleus. Emits a: 7 N β- particle (negative charged), and Anti-neutrino (no charge) 0 14 Beta (β-) Decay β- -1 6 C ̅νe (anti-neutrino) Beta Plus (β+) Decay When a nucleus has too many protons A proton converts into a neutron inside the nucleus. Emits a: β+ particle (aka Positron (e+ )) (positive charged), and Neutrino Beta Plus (β+) Decay When a nucleus has too many protons A proton converts into a neutron inside the nucleus. Emits a: β+ particle (aka Positron (e+ )) (positive charged), and Neutrino Beta Plus (β+) Decay When a nucleus has too many protons 22 A proton converts into a neutron inside the nucleus. Emits a: 10 Ne β+ particle (aka Positron (e+ )) (positive charged), and Neutrino (no charge) 0 22 Beta (β+) Decay β+ 1 11 Na (positron) ve (neutrino)  Common Sources of α, β-, and β+ Particles Ionisation Power Sources α High Heavy, unstable nuclei (e.g. uranium-238, radium-226, thorium-232) β- Nuclei with an excess of neutrons (e.g. carbon-14, strontium-90) Medium β+ Nuclei with an excess of protons (e.g. isotopes like carbon-11, fluorine-18) Isotopes = Atoms with the same number of protons but different numbers of neutrons. They share almost the same chemical properties, but differ in mass and therefore in physical properties. There are stable isotopes, which do not emit radiation, and there are unstable isotopes, which do emit radiation. Penetrating Power of Particles  Note: Gamma radiation is NOT a particulate ionisation, but electromagnetic ionisation. Unlike alpha and beta particles, gamma rays have no mass or charge. Gamma radiation is not a particles but an electromagnetic wave. α,β,γ radiation are frequently mentioned together because they are commonly emitted by radioactive materials, especially during nuclear decay processes, even though γ radiation is electromagnetic. Post-lecture questions What is the wavelength of a radio wave transmitting at 98.3MHz? Post-lecture questions What is the wavelength of a radio wave transmitting at 98.3MHz? It looks like there is only one piece of information in the question, but it says that the wave is a radio wave, and all radio waves (and EM waves) travel at the speed of light 3×108ms−1. v = 3×108ms−1 f = 98⋅3MHz=98⋅3×106Hz v=? v=f×λ 3×108 = 98.3 × 106 × λ λ = 3×108 ÷ 98.3×106 λ = 3.05m Post-lecture questions Post-lecture questions Emitted Charges of the particles emissions Post-lecture questions Positive Negative & no charge & Anti-neutrino - Positive & no charge & Neutrino + (positron) A nucleus with 84 protons and 126 neutrons undergoes alpha decay. It forms lead. Outline the Decay Equation. A nucleus with 84 protons and 126 neutrons undergoes alpha decay. It forms lead. Outline the Decay Equation. A nucleus with Carbon-14 undergoes beta decay. Outline the Decay Equation. A nucleus with Carbon-14 undergoes beta decay. Outline the Decay Equation. A nucleus with Carbon-10 undergoes beta decay. Outline the Decay Equation. A nucleus with Carbon-10 undergoes beta decay. Outline the Decay Equation. 10 10 Knowledge Check - Electromagnetic Spectrum and Particle Radiation Can you describe and explain: The properties of the Electromagnetic Spectrum (Definition and components of the electromagnetic spectrum. Wavelength, frequency, and energy relationships; mention the seven types of EM waves, and their common uses in daily life and medicine). The properties of Particle Radiation (Specifically, alpha particles, beta particles, neutrons, and protons; Basic properties and sources). Differences between particle and electromagnetic radiation will also be highlighted. References + Resources Lemons, D.S. 2017. Drawing Physics: 2,600 years of discovery from Thales to Higgs. MIT Press. Hutchings, R. and Hackett, R. 2008. OCR Physics AS Level Student Book. Pearson Education Ltd. Bushong, S.C., 2020. Radiologic science for technologists. Elsevier Health Sciences. National Aeronautics and Space Administration, Science Mission Directorate. (2010). Anatomy of an Electromagnetic Wave. Retrieved [Sept 10, 2024], from NASA Science website: http://science.nasa.gov/ems/02_anatomy The wave equation - Wave parameters and behaviours - National 5 Physics Revision - BBC Bitesize Questions - frequency and time period - Amplitude, wavelength and frequency - CCEA - GCSE Physics (Single Science) Revision - CCEA - BBC Bitesize Calculating wave speed - Features of waves – WJEC - GCSE Physics (Single Science) Revision - WJEC - BBC Bitesize The Electromagnetic Spectrum | HubbleSite Infrared Waves - NASA Science Visible Light - NASA Science Ultraviolet and electromagnetic waves in medicine - Light and electromagnetic waves - Edexcel - GCSE Combined Science Revision - Edexcel - BBC Bitesize X-Rays - NASA Science https://doi.org/10.1016/B978-0-12-809486-0.00004-2 Particle, wave, both or neither? The experiment that challenges all we know about reality (nature.com) https://www.iaea.org/newscenter/news/what-are-isotopes Hay, G.A. and Hughes, D.J., 1978. First-year physics for radiographers. Baillière Tindall. Carlton RR, Adler AM. Principles of radiographic imaging: an art and a science, 3rd ed. Delmar Publishers; 2001. https://jackwestin.com/resources/mcat-content/atomic-nucleus/radioactive-decay-2 https://www.savemyexams.com/a-level/physics/ocr/17/revision-notes/6-particles--medical-physics/6-8-fundamental-particles/6-8-4-beta-minus--beta-plus-decay/ https://www.savemyexams.com/gcse/physics/aqa/18/revision-notes/4-atomic-structure/4-2-atoms--nuclear-radiation/4-2-4-alpha-decay/