The phenomenon of interference and diffraction establish that light travels in the form of waves. It may reasonably be questioned that whether the light waves are longitudinal or transverse. There are number of evidences which indicate that the light waves are transverse in nature. The group of experimental study confirmed that light waves are transverse in nature. This property of light is called polarisation of light. Polarisation means departure from complete symmetry of wave about the direction of propagation.
The phenomenon of polarisation of light was discovered by Huygene in 1690. Light can be obtained which lacks symmetry around the direction of propagation. It proves the transverse nature of light waves because longitudinal waves cannot show different properties in the different directions perpendicular to the direction of propagation.
This chapter aim to enable students describe phenomenon of polarization and explain how polarization of light explains the transverse nature of light. In addition, this chapter helps students state Brewster's law and make them able to use it in different areas. At the end of the chapter, both numerical and conceptual questions have been solved and the exercises, including multiple-choice questions, are included to make students' learning effective and clear their doubts.
Polarization Complete Note for IOE
1. Polarisation of light
The light which acquires the property of one-sidedness is called polarised light and this phenomenon is called polarisation of light. The phenomenon of confining the vibration of a the wave in a specific direction perpendicular to the direction of wave motion is called polarization.The plane containing the direction of vibration and wave motion is called plåne of polarization.
2. Brewster's Law
According to this law, when polarized light is incident at polarizing angle, iP, on an interface separating air from a medium of R.I. , then the reflected light is fully polarized provided
3. Malus Law
According to this law, when a beam of completely polarized light is incident on an analyser, the resultant intensity of light (I) of transmitted light from the analyser varies directly as the square of the cosine of the angle between plane of transmission of analyze and polarizer i.e.Polaroid:
A Polaroid is a material which polarizes light. Tourmaline is a natural polarizing material Polaroids are now artificially made ex - quinine idosulphate
Optical rotates
It is the phenomenon of rotating the plane of polarization light about the direction of propagation of light when passed through solution contain crystal. The substances which rotate the plane of polarization are said to be optically active Examples: quartz, sugar crystal, sodium chloride, turpentine oil etc.
Top 20 short Questions of Polarization
1. What is polarization?
Ans.: Polarization refers to the direction in which the electric field of an electromagnetic wave oscillates.
2. What is the difference between linear and circular polarization?
Ans: In linear polarization, the electric field of the wave oscillates in one direction, while in circular polarization, it rotates in a circular manner.
3. How is polarization used in sunglasses?
Sunglasses use polarizing filters to block out glare and reduce the intensity of light by selectively allowing only vertically polarized light to pass through.
4. How does polarization affect light transmission through a material?
Polarization can affect the amount of light that is transmitted through a material. If the polarization of the light is not aligned with the polarization of the material, some of the light will be absorbed or reflected, reducing the overall intensity of the transmitted light.
5. What is the polarization angle of unpolarized light?
The polarization angle of unpolarized light is random and continuously changes with time.
6. What is the difference between polarized and unpolarized light?
Polarized light has a fixed direction of polarization, while the direction of polarization of unpolarized light is random and continuously changes.
7. What is the effect of polarization on the reflection of light?
When light is reflected at a certain angle, it becomes polarized. The amount of polarization depends on the angle of incidence and the refractive index of the materials involved.
8. How does polarization affect the visibility of LCD screens?
LCD screens use polarizers to control the amount of light that passes through each pixel. The polarizers can be adjusted to control the polarization of the light, which affects the overall brightness and contrast of the screen.
9. How can polarization be used to measure stress in materials?
Polarization can be used to measure stress in materials by measuring changes in the polarization of light that passes through the material as the material is subjected to stress.
10. What is the relationship between polarization and birefringence?
Birefringence is the property of materials that causes them to refract light differently depending on the polarization of the light. Materials with high birefringence can be used to create polarizers and other polarization optics.
11. How does polarization affect the scattering of light?
The polarization of light affects the way it scatters off of objects. Light that is scattered at certain angles becomes polarized, with the degree of polarization depending on the angle of scattering and the refractive index of the material.
12. What is polarimetry and how is it used?
Polarimetry is a technique for measuring the polarization of light. It is used in a variety of applications, including materials science, biochemistry, and astronomy.
13. How does polarization affect the behavior of electromagnetic waves in waveguides?
The polarization of electromagnetic waves affects the way they propagate through waveguides. Some types of waveguides are designed to only allow waves with certain polarization states to propagate.
14. What is the Poincaré sphere and how is it used in polarization optics?
The Poincaré sphere is a mathematical tool used to visualize and analyze the polarization of light. It is used in a variety of applications in polarization optics, including in the design of polarizers and waveplates.
15. What is the Malus law and how is it used in polarization measurements?
The Malus law describes the relationship between the intensity of polarized light and the angle between the polarization direction and the transmission axis of a polarizer. It is used in polarization measurements to calculate the degree of polarization of a sample.
16. How does polarization affect the interference of light?
Polarization can affect the interference of light by altering the phase difference between two waves. Waves that are polarized in the same direction can interfere constructively or destructively, depending on the phase difference between them.
17. How does polarization affect the absorption of light by molecules?
The polarization of light can affect the way it is absorbed by molecules. Molecules can absorb light that is polarized in certain directions more readily than light that is polarized in other directions.
18. How can polarization be used in optical communication?
Polarization can be used in optical communication to transmit multiple channels of data simultaneously over a single fiber. By using different polarizations for each channel, multiple signals can be transmitted and separated at the receiving end.
19. How does polarization affect the performance of radar systems?
Polarization can affect the performance of radar systems by altering the way that electromagnetic waves are reflected and scattered by objects. By using different polarizations, radar systems can be optimized for specific applications.
20. How can polarization be used in remote sensing applications?
Polarization can be used in remote sensing applications to identify and characterize different types of materials based on their polarizing properties. For example, polarimetry can be used to distinguish between different types of vegetation or to detect oil spills on water surfaces.
