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Light and Matter Interactions
Montāžas Teksta
- Slidkalniņš: 1
- Professor, What is Light and Matter Interactions?
- Slidkalniņš: 2
- Light and matter interactions is basically just the process of how light influences or gets influenced by matter.
- Slidkalniņš: 3
- For example, things like Light being scattered, refracted, transmitted or even being reflected, are just some examples of light interacting with matter.
- Slidkalniņš: 4
- Of Course!
- Can you explain those four examples in a bit more detail?
- Slidkalniņš: 5
- Let's start with Light being scattered. This is the process in which Light deviates from a straight trajectory path.
- Ahh, so it's kind of like Reflection.
- - bns.institute/applied-sciences/scattering-of-light-explained/
- Slidkalniņš: 6
- Not necessarily, you see reflection reflects the light in a single path that is predictable, and scattering redirects the light in multiple directions that are unpredictable
- One example of light being scattered is the Light that we get from the sun as it hits the Earth's atmosphere, leading to a certain phenomena that creates the blue sky that we see every day
- https://bns.institute/applied-sciences/scattering-of-light-explained/
- Slidkalniņš: 7
- All of the colors in the visible spectrum are in the sunlight that passes through the atmosphere. The shorter wavelengths like Blue and Violette scatter more efficiently than other colors like red or green
- How does it do that?
- In-class notes
- Slidkalniņš: 8
- https://learn.sait.ca/d2l/le/lessons/800122/topics/19677968
- Particle
- Light Enters the atmosphere
- As you can see, when the sunlight comes into contact with the molecules and particles in the air, it causes the wavelength that is associated with the blue colour to scatter, since the particle is really small compared to the wavelength
- How did we get outside, and on the roof?
- Light gets scattered
- This type of scattering is called Rayleigh scattering
- Slidkalniņš: 9
- This happens because the EM energy gets absorbed and then gets emitted in discrete units, these units are called photons or "quanta"
- - In class notes
- Slidkalniņš: 10
- The formula we use is as follows:Q=hv
- h is Plancks Constant
- v is the Frequency
- The Q value is the Radiant energy
- - In class notes
- Slidkalniņš: 11
- Next up is Reflection. This is caused when light does not get absorbed by matter and it just reflects back outwards, perpendicular to the angle in which it hit it in
- Like I said before, Reflection and scattering are similar in the way that they both get bounced off the object, however the angle after the light gets reflected in is predictable and when its scattered its not.
- https://science.nasa.gov/mission/webb/science-overview/science-explainers/spectroscopy-101-light-and-matter/
- Slidkalniņš: 12
- Wavelength of Colours
- https://science.nasa.gov/mission/webb/science-overview/science-explainers/spectroscopy-101-light-and-matter/
- Slidkalniņš: 13
- Now lets talk about what happens when light doesn't get reflected in any way. One example of this is called Refraction. Does anyone want to take a guess as to what this is
- I know what it is!
- Slidkalniņš: 14
- Refraction happens when light passes through an object with a different temperature or density, this causes the speed of the light to change and therefore causing it to exit the object in a different direction
- - In class notes
- Slidkalniņš: 15
- M.1
- Slows down
- M.2
- Speeds up
- M.3
- - In class notes
- Let's say there are 3 mediums, The light enters the firsts medium at normal speed and when it leaves it slows down causing the light to bend closer to the horizontal line. Now the same scenario happens in medium 2, however this time the light speeds up, this causes the light to bend closer to the vertical line
- Slidkalniņš: 16
- An example of this is snow. The main reason why snow is white is because it reflects all colours in visible light extremely well causing it to have an appearance of white.
- The Equation that best represents the refractive index of a medium is as follows:
- n = c/v
- The value of v is the speed of light in the medium
- The n value is simply just the refractive indices
- The value of c is the speed of light in a vacuum
- -Scienceinfo.com/refraction-of-light/
- Slidkalniņš: 17
- Very Very good! Ok, last but not least there's Transmission. Unlike Refraction, Transmission is the process in which the light just passes straight through, it doesn't bend, slow down or speed up.
- https://science.nasa.gov/mission/webb/science-overview/science-explainers/spectroscopy-101-light-and-matter/
- Slidkalniņš: 18
- Light/Wavelength
- Window
- https://science.nasa.gov/mission/webb/science-overview/science-explainers/spectroscopy-101-light-and-matter/
- This happens because the matter does not absorb, reflect or influence the wavelength/light in anyway. For example, a window. The reason why a window is transparent is because it transmits all colours of visible light and doesn't absorb it
- Slidkalniņš: 19
- But, how does all of this relate to remote sensing?
- Slidkalniņš: 20
- You see every single day the EM radiation from the sun hits the surface of the earth causing the 4 phenomena's we just talked about. In remote sensing we can think of it as light rays, as they hit the earth or objects they bounce back to a sensor that is in orbit (This is the energy they detect)
- https://gisgeography.com/energy-interaction-remote-sensing-light-reflection-absorption-transmission/
- Slidkalniņš: 21
- For Refraction, as you know when light passes through an object it changes its direction based on the density of the object, in remote sensing this phenomena affects how the sensor perceives the object.For Scattering there are 3 different types of it:-Rayleigh Scattering (Which was explained earlier)-Mie Scattering, Which is when the Wavelength and particle are the exact same sizeNon-Selective Scattering, which is when the particle is much larger than the wavelength
- - In class notes
- Slidkalniņš: 22
- And as for Transmission, it uses atmospheric windows to allow the radiation from the surface to reach the sensorsAtmospheric windows: Something that allows the radiation to pass straight through the atmosphere without being absorbed.
- https://gisgeography.com/energy-interaction-remote-sensing-light-reflection-absorption-transmission/
- Slidkalniņš: 23
- References
- - Scienceinfo.com/refraction-of-light/- bns.institute/applied-sciences/scattering-of-light-explained/- science.nasa.gov/mission/webb/science-overview/science-explainers/spectroscopy-101-light-and-matter-gisgeography.com/energy-interaction-remote-sensing-light-reflection-absorption-transmission/-https://learn.sait.ca/d2l/le/lessons/800122/topics/19677969-Class notes from Carina
- Slidkalniņš: 24
- Thank you for Reading!
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