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1. What is Polarimeter?
It is a device used to measure the angle of rotation of plane of polarization rotated by an optically active substance.
2. What is specific rotation?
Specific rotation of an optically active substance at a given temperature is the rotation in degrees of the plane of polarization of incident polarized beam produced by one decimeter length of substance of unit concentration.
3. What do you mean by polarization?
The lack of symmetry about the direction of propagation of light is known as the polarization of light.
4. What are optically active substances?
Optically active substances rotate the plane of polarization or plane of vibration of plane polarized light when it passes through it.
5. What are different optically active substances?
Right handed or dextro & left handed or leavo rotatory.
6. What is the function of analyzer and polarizer?
Polariser changer ordinary light to plane polarised light and analyzer is used to analyse light emitted through the optically active substance.
7. What is Bi-quartz device?
It consists of two semicircular disc of right handed and left handed quartz which are cemented together to form a circular disc.
8. How does specific rotation depend on temperature?
In some substances it decreases with rise in temperature like turpentine while in quartz it increases.
9. What is the unit of specific rotation?
degree/decimeter/gm/cc
10. Name one practical use of polarimeter.
It is used to measure percentage of sugar in a solution.
11. What is Brewster's law of polarization?
The tangent of the polarizing angle is mathematically equal to the refractive index of the material i.e µ = tan (ip)
12. Define plane of vibration and plane of polarization.
The plane of polarization is that plane in which no vibrations occur and the plane in which vibrations occur known as plane of vibration. The vibrations occur at the right angle to the plane of polarization.
13. What do you mean by double refraction?
When a ray of light is refracted by a crystal of calcite it gives two refractive rays .this phenomenon is known as double refractions.
14. What is nicol prism?
It is an optical device which is made by calcite crystal to produce and analyze the plane polarized light.
15. What do you mean by Snell's law?
The sine of the angle of incidence to sine of the angle of refraction is equal to the refractive index of the material.
16. What is mean by plane polarized and unpolarized light?
The plane polarized light is the light in which the vibrations take place only along one straight line perpendicular to the direction of propagation of light while in unpolarized light vibrations take place along all possible straight lines perpendicular to the direction of propagation of light.
17. What are the ordinary and extra ordinary lights?
Ordinary light obeys Snell’s law while extra ordinary doesn’t obey the Snell’s law.
18. Define refractive index?
It is the ratio of velocity of light in vacuum to the velocity of light in any medium. µ = c/ v
19. What do you mean by right handed or dextro rotatory and left handed or laevo rotatory substances?
The substance that rotates the plane of polarization (or plane of polarization) in the clockwise direction as seen by an observer facing the emergent light is said to be right handed or dextro-rotatory.
20. Give few example of above two type of substance?
The example of right handed or dextro rotatory substance are, the solution of camphor in alcohol, cane sugar (without crystalline structure). Glucose, solution of tartaric acid in water, amorphous tartaric acid, d-quartz etc. The left handed or laevo rotatory substance are, fructose, nicotine, turpentine oil and 1 quartz.
21. What do you mean by optically inactive substance? Give one or two examples?
Optically inactive substance are those, when a plane polarized light passes through them its plane of polarization (or plane of vibration) remains unrotated. Thus the plane of polarization of emergent beam is same as that of incident polarized beam. The examples of optically inactive substances are, fused quartz (quartz in an amorphous form), calcite etc.
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