When a beam of ordinary light is passed through a calcite crystal, the light splits into O-ray and E-ray inside the crystal.
Both E-ray and O-ray are polarised
Calcite Crystal and Light Polarization
When a beam of ordinary light, which is unpolarized, enters a calcite crystal, it undergoes a unique optical phenomenon known as double refraction or birefringence. This means the incident light ray splits into two distinct rays inside the crystal. These two rays are known as the Ordinary ray (O-ray) and the Extraordinary ray (E-ray).
Understanding O-ray and E-ray
- O-ray (Ordinary Ray): This ray behaves like a normal light ray. It obeys Snell's law of refraction and travels with the same speed in all directions within the calcite crystal. Its wavefront is spherical.
- E-ray (Extraordinary Ray): This ray behaves differently. It generally does not obey Snell's law, and its speed varies with direction within the calcite crystal. Its wavefront is ellipsoidal.
Polarization State of O-ray and E-ray
A crucial aspect of double refraction is the state of polarization of these two rays. Although the incident ordinary light is unpolarized, both the O-ray and E-ray that emerge inside the calcite crystal are found to be plane polarized.
- The O-ray is plane polarized with its vibrations perpendicular to the principal plane of the crystal.
- The E-ray is also plane polarized, but its vibrations are parallel to the principal plane of the crystal.
Therefore, the planes of vibration for the O-ray and E-ray are mutually perpendicular to each other. This distinct polarization of both rays is a defining characteristic of light passing through birefringent crystals like calcite.
Conclusion on Light Splitting and Polarization
When unpolarized ordinary light passes through a calcite crystal, the initial unpolarized light is effectively resolved into two components, each of which is plane polarized. One component forms the O-ray, and the other forms the E-ray. Both these rays are polarized, with their planes of vibration at right angles to each other.
Thus, the statement that both E-ray and O-ray are polarised is accurate, reflecting the fundamental principles of crystal optics and light polarization.
Important Questions from Polarisation
For light incident from air onto a transparent dielectric surface, the Brewster's angle $i_b$ is determined by the refractive index $n$ of the dielectric medium according to $\tan(i_b) = n$. Considering typical transparent dielectric materials, which generally have $n > 1$, what is the characteristic range for $i_b$?
A beam of transverse waves whose vibrations occur in all directions perpendicular to their direction of motion is
Which property of light shows it is a transverse wave ?
Which of the following phenomena is not common in light and sound wave?
Which of the following phenomena establishes the transverse nature of light waves?
