How Does Scattering Cause Light Polarization?
We see that the charges occurring in a molecule are oscillating then we say that along the y-axis it will not radiate along the y-axis. Therefore here we conclude that at 90° away from the beam direction the scatter which is by the light is linearly polarized. This is concluded to cause the light which generally undergoes Rayleigh scattering from the blue sky to be partially polarized.
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How Sunlight is Polarised
The light which is said to be an unpolarized light that is said to be passing through a fluid is scattered that is the scattered light which is being partially or completely plane polarized. For the light to get the effect of scattering by particles of comparable size to the wavelength of the light we can say that this process is known as rayleigh scattering. The wavelength that is said to be generally dependent on this type of scattering is responsible for blue skies and red sunsets.
the light which is said to be the unpolarized white light which is from a slide projector enters a fish tank of very slightly milky water. Some of the waves which are known as the electromagnetic waves impinging on the colloidal particles and molecules in the water are said to be absorbed and re-radiated. The horizontal component that we have seen here is we can say of the polarization decreasing as cos2θ that is where θ is the scattering angle. We can hear see that the maximum scattered intensity is perpendicular to the plane, that is we can say of oscillation of the molecule which is where it is also totally plane polarized, θ=90°. At the angles which are the other angles the light is partially plane polarized.
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To show this whole phenomenon we can say that the audience generally observes the tank at right angles to the initial direction which is the propagation of the light. A mirror which is said to be angled over the tank generally allows them to see scattered light emerging from two surfaces which are said to be perpendicular to each other we can easily observe it in the figure . The rotating which occurs in the Polaroid 90° blocks the light from the top of the tank but now we can say that the scattered light from the side of the tank reappears. Alternatively here we will say that or suppose that let the scattering process polarize an unpolarized beam from the slide projector and let the Polaroid sheet be the analyzer .
Rayleigh the phenomenon which is of the scattering has a wavelength dependence of 1/(λ4) so we can say that it generally affects blue light much more strongly than red. By adding the tank which is of milk to the tank we increase the scattering phenomenon the milky water begins to develop a bluish tint and the unscattered beam reddish.
Polarisation by Refraction
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The is the kind of action that generally takes place in a 5 gallon fish tank. The mirror that is said to be 1m × 0.75m is hinged and its base can be clamped to a cart so we can say that the mirror then leans on the tank. The mirror which generally should be angled to give the center rows that is said to be of the audience which is of the optimum view of the upper surface of the tank so we can say that this puts it at over 45° and unfortunately we can say that the view is not perfect for the front and back of the hall. Provide there is a beaker of milk and a pipette which is to add milk to the tank. The water which generally may be dirty enough initially to scatter well without adding milk. For a slide projector which we generally use a Beseler Slide King as it has a powerful 1000W bulb and along with that it holds a load with a 5cm circular aperture slide to simulate the Sun. It can also be said that it sit on the cart too but leaves a small distance between it and the tank so you can insert the Polaroid. The unscattered light that should generally fall onto a projection screen that is several meters ahead of the cart should be angled so that the audience can see the spot.
So here we need to be a bit careful not to add too much milk that is as multiple scattering which will occur and wash out the color effect as well as the polarization. The symbol which is said to be denoted as λ-4 dependence is only valid if the scattering objects are smaller or comparable in size to the wavelength of the light. So it generally works for nitrogen and oxygen molecules but this is not for water droplets which are much larger than the symbol which is λ and scatter all colors equally so hence we can say that the clouds are white.
Polarisation by Scattering
A light wave which is also said to be an electromagnetic wave that travels through the vacuum of outer space. The waves which are of light are produced by vibrating electric charges.
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The transverse nature of an electromagnetic wave is said to be quite different from any other type of wave that has been discussed in The Physics Classroom Tutorial. So now Let's here suppose that we use the customary slinky to model the behavior of an electromagnetic wave. An electromagnetic wave is said to travel towards us and then we would observe the vibrations of the slinky occurring in more than one plane of vibration.
FAQs on Polarization by Scattering Explained
1. What is meant by polarization of light by scattering?
Polarization by scattering is a phenomenon where unpolarized light becomes polarized after being scattered by small particles. When sunlight, which is unpolarized, strikes molecules in the Earth's atmosphere (like N₂ or O₂), the electrons in these molecules absorb the light and re-radiate it in various directions. The scattered light, when observed at a 90-degree angle to the direction of the incident sunlight, is found to be plane-polarized. This happens because the oscillating electrons cannot radiate energy along their line of oscillation.
2. What is a common real-world example of polarization by scattering?
The most common example is the partially polarized light from the blue sky. When you look at a part of the sky that is 90 degrees away from the sun's position, the scattered sunlight you see is strongly polarized. You can verify this by looking at the sky through a polarizing filter (like polarized sunglasses) and rotating it. You will notice the brightness of the sky change, confirming that the light is polarized. This principle is used by photographers to darken the sky and enhance clouds in pictures.
3. Why is light from the clear blue sky polarized?
The light from the sky is polarized due to the fundamental mechanism of Rayleigh scattering. Here’s a step-by-step explanation:
- Sunlight is an electromagnetic wave with its electric field oscillating in all directions perpendicular to its path. This is unpolarized light.
- When this light hits an air molecule, it forces the electrons in the molecule to oscillate.
- These oscillating electrons act like tiny antennae, re-radiating the light. However, an oscillating charge does not radiate energy along its axis of oscillation.
- For an observer looking at the sky at a right angle (90°) to the sun, the only electric field vibrations they see are the ones oriented perpendicular to both their line of sight and the sun's rays. Vibrations along the line of sight are not radiated towards the observer.
- This restriction of vibrations to a single plane results in plane-polarized light.
4. How does polarization by scattering differ from polarization by reflection?
While both are methods to polarize light, they operate on different principles:
- Mechanism: Polarization by scattering involves the absorption and re-radiation of light by particles smaller than the light's wavelength. Polarization by reflection occurs when light bounces off a non-metallic surface, like water or glass.
- Condition for Maximum Polarization: In scattering, polarization is maximum when viewed at an angle of 90° to the incident light. In reflection, maximum polarization occurs at a specific angle of incidence known as Brewster's angle, which depends on the refractive index of the material.
- Resulting Light: In scattering, the scattered light is polarized. In reflection, the reflected light is polarized, and the refracted light is partially polarized.
5. What is the fundamental difference between unpolarized and linearly polarized light?
The fundamental difference lies in the orientation of the electric field vibrations.
- In unpolarized light, the electric field vector oscillates in all possible directions perpendicular to the direction of wave propagation. Natural light from sources like the sun or a bulb is unpolarized.
- In linearly polarized light (or plane-polarized light), the electric field vector is confined to oscillate in only a single plane along the direction of propagation. This creates a more orderly wave structure.
6. What factors affect the intensity and polarization of scattered light?
Several factors are crucial for polarization by scattering:
- Size of Scatterer: For efficient polarization via Rayleigh scattering, the scattering particles (e.g., air molecules) must be significantly smaller than the wavelength of the incident light. If particles are larger, Mie scattering occurs, which does not produce strong polarization.
- Angle of Observation: The degree of polarization is highly dependent on the viewing angle. It is zero in the forward and backward directions and maximum at 90° with respect to the incident beam.
- Wavelength of Light: According to Rayleigh's law, the intensity of scattered light is inversely proportional to the fourth power of the wavelength (I ∝ 1/λ⁴). This is why blue light scatters more than red light, making the sky appear blue, but it doesn't directly alter the polarization state itself, only the intensity of the polarized component.
7. Can light be 100% polarized by scattering in the atmosphere?
In theory, light scattered at a perfect 90-degree angle from a single, small molecule would be 100% linearly polarized. However, in the Earth's atmosphere, the light we observe is only partially polarized, not 100%. This is due to several factors, primarily multiple scattering. Light that reaches our eyes has often been scattered more than once by different molecules from different directions. This mixing of light from various scattering events and reflections from the ground and dust particles reduces the overall degree of polarization.
