KAN Talks 4: Electromagnetic Radiation
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Lohith will gives a brief overview of what electromagnetic radiation is all about. About the speaker: Lohith is 14 years old and is a part of Mango Astronomy club. He is passionate about physics.
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KAN Talks 4: Electromagnetic Radiation
- 2. Schlumberger-Private Electromagnetic Radiation A vision of EVERYTHING!!!
- 3. Schlumberger-Private Intro ▪ It is nothing but a form of energy travelling in the form electric and magnetic waves moving simultaneously. ▪ It is the second strongest force out of the four.
- 4. Schlumberger-Private Electromagnetic Spectrum • It is a wide range of lights of different wavelengths. • A spectrum is literally limitless and as the frequency increases the energy of the photon increases proportionally.
- 5. Schlumberger-Private Photo ns • Photons are the particles of light. • Photon is actually a wavicle. • Different frequency photons exhibit different types of light In the electromagnetic spectrum.
- 6. Schlumberger-Private Photoelectric effect • It is the famous theory for which Albert Einstein got awarded with the Noble Prize. • It says that when light(generally UV) is shone on a metal it emits electrons. • This theory helped in the wave-particle duality.
- 8. Schlumberger-Private Cosmic Microwave Background • CMB is the Electromagnetic remnant of the Big Bang. • The intense high frequency radiation got red shifted into microwaves. • The recording of CMB in the sky has led to the creation of the universal map using the Wilkinson Microwave Anisotropy Probe.
- 9. Schlumberger-Private Doppler Effect • Doppler effect is a phenomenon found in waves when their origins move very fast towards or away from the receiver. • If the origin moves towards the receiver then the waves get compressed reducing the wavelength resulting in increase in the frequency called Blue-Shift. • If the origin moves away from the receiver then the waves get expanded increasing the wavelength resulting in reduction in the frequency called Red-Shift. • Example of such phenomena:
- 10. Schlumberger-Private Doppler Effect • It is also seen in sound waves. • This is the reason for Cherenkov radiation and sonic boom.
- 11. Schlumberger-Private Cherenkov Radiation • Light is the fastest thing in vacuum and its speed is called the cosmic speed limit but certain particles are faster than light in other mediums. • Electron is faster than light in D2O i.e Heavy Water. So as electron also emits and reflects light, it is an origin of light waves. This results in total compression of waves in front of the electron due to doppler effect. • This emits an different type of radiation called Cherenkov radiation.
- 13. Schlumberger-Private LASERS • LASER-Light Amplification by Stimulated Emission of Radiation. • Laser is nothing but emitting an amplified and focused single-frequency beam of light. • The general absorption and emission of light by an atom is called spontaneous emission of light. • Whereas stimulated emission of radiation is about emitting a photon in the presence of a another one which is similar to this in the means of frequency,amplitude,phase,polarization.
- 14. Schlumberger-Private LASERS • For this the electron in the excited state should pause at its metastable state non-radiatively and then further cascade to its ground state.
- 15. Schlumberger-Private Yarkovsky Effect • This is the key to the human race for quick transportation of tiny probes to another star system. • This is the propulsion of objects using momentum of light when an object’s surface heats up, it gains energy and it cools down by emitting photons, this helps in its propulsion. • In future there is a plan of sending tiny chips with lenseless cameras to Alpha centauri at 20% the speed of light.
- 17. Schlumberger-Private Rayleigh effect• The sky’s blue colour and blood moon’s red colour all has a reason that is nothing but Rayleigh effect. • The blue colour gets scattered in the sky giving its colour an blocking this wavelength from reaching eclipsed moon. •This is called the “Blood moon effect”.
- 18. Schlumberger-Private Absorption and emission of light • Light interacts with an atom by exciting the an electron and pushing it to a higher orbit. • The excited electron again returns back to its ground or mean state by emitting a photon.
- 19. Schlumberger-Private Absorption and emission spectrum • Few elements absorb certain wavelengths of light and emit them. • So certain colours of the Total spectrum won’t be visible. And they will be emitted while the electrons of the element return to their ground states. • The band of colours obtained after absorption is called absorption spectrum and the one obtained on emission is called emission spectrum. • Each element has its own spectrum. • When white light passes through a planet’s atmosphere, the elements absorb certain wavelengths through which we can find out the atmospheric composition.
- 21. Schlumberger-Private Virtual Photons • Virtual photons are simple photon like disturbance in the electromagnetic ield. • An real photon is a real thing that has an inluence on quantum electromagnetic ield and is stronger and much longer than virtual disturbances. • These virtual photons are the actual medium of Electromagnetic force.
- 22. Schlumberger-Private Epoch of reionisation • The early universe was small and illed with hydrogen atoms. • These atoms didn’t allow light to pass through them leaving the universe dark. • With the formation of the irst galaxies the hydrogen atoms started to get illed up with energy leaving no space for more this paved up the way for the irst photon to travel out of the huge cloud into free space. • The period during which this event occurred is called the epoch of reionisation. • Astronomers cannot see any incident that occurred before this reionisation through electromagnetic techniques like telescopes.