Duduli

A compensator is an optical device whose function is to compensate a path difference. It is used in conjunction with a polarizer and analyzer combination to investigate elliptically polarized light.

Incoherent waves are the waves that do not maintain a constant phase difference. Then the phase of the waves fluctuate irregularly with time and independently of each other. In case of light waves the phase fluctuates randomly at a rate of about 10⁸ per second.

Bessel functions are a set of solutions for differential equations of a  certain type. These are useful to obtain propagation characteristics of electromagnetic waves in circular wave guides. The solutions for the Bessel function are obtained for certain values of Kc.

According to Nernst, “ The heat capacities of all solids tend to zero as the absolute zero of temperature is approached and that the internal energies and entropies of all substances become equal there, approaching their common value asymptotically tending to zero ”.  Usually it is called as third law of thermodynamics.

When two bodies are approaching each other, a force comes into play between them for a finite time and brings about a measurable change in their velocities, momenta and energy according to the respective laws of conservation, a collision is said to have taken place.

A Spherical lens, which is free from the defects of spherical aberration and coma is called an aplanatic lens. A pair of conjugate points free from spherical aberration and coma is called aplanatic points.

The number of microstates corresponding to any given macrostate is called its thermodynamic probability. In other words, the thermodynamic probability of a particular macrostate is defined as the number of microstates corresponding to that macrostate. In general, this is a very large number and is represented by W.

By the passage of electric current through a thermocouple with junctions initially at the same temperature, difference of temperature is developed between the two junctions. This effect is known as peltier's effect.

It states that the velocity of efflux of liquid from an orifice at a certain depth in a tank is equal to the velocity of a body acquired in falling freely from the free surface of the liquid upto the orifice.

It states that “ If an ideal liquid (i.e incompressible and non-viscous) flows through a tube in streamline motion, then the product of cross-sectional area of tube and velocity of flow is same at every point in the tube”.      Mathematically,                   AV=Constant Where , A = area of the cross section               V = velocity of the liquid

It states that the ratio of the emissive power to the absorptive power for a given wavelength at a given temperature is the same for all bodies and is equal to the emissive power of a perfectly black body at that temperature.

A body that emits light on account of high temperature is called incandescent. There are bodies that emit light due to causes other than high temperature and they are said to be luminescent.

Malus's law states that “ intensity of polarized light transmitted through a polarizer is proportional to the square of cosine of the angle between the plane of polarization of the light and the transmission axis of the polarizer”.

Photoelectric effect is the phenomenon in which electrons are knocked off a metal surface when light is incident on it. The metal is said to be a photosensitive material and the liberated electrons are called photoelectrons.

Increase in refractive index with increase in wavelength is termed as anomalous dispersion. It is noticed that anomalous dispersion is present at those wavelengths corresponding to the absorption bands of the medium. For example, in the case of sodium vapour in the visible region, anomalous dispersion is noticed at wavelengths 5890 Å and 5896 Å.

We know,  Path difference between two consecutive reflected ray is, ∆ = 2μtcosr + λ/2       Here r = 0       I.e cosr =1 For central fringe t = 0   So  ∆ = λ/2     i.e path difference is the odd multiple of λ/2 therefore central fringe in Newton's ring is dark.

It consists of two plano-convex lenses of equal focal lengths. The distance between the two lenses is equal to the focal length of either lens. The convex surfaces of both the lenses face the incident light.

In Newton's ring arrangement, a thin air film is enclosed between a plano-convex lens and a glass plate. A given order of maxima or minima will be obtained for particular value of thickness of air film, which remains constant along the circumference of circle. So circular fringes are obtained in Newton's ring.

Optically inactive substances acquire the ability of rotating the plane of polarization of light when they are subjected to a magnetic field, parallel to propagation direction. Michael Faraday discovered this effect and hence it is called Faraday effect. This effect occurs in most optically transparent dielectric materials (including liquids) when they are subject to strong magnetic fields.

In a simple pendulum, bob moves on a circle but a pendulum in which bob is constrained to move on a sphere rather than on a circle is called spherical pendulum. The position of the bob is located by spherical co-ordinate θ , φ as shown in figure. The distance r of the bob from the origin will be the radius of the sphere on which the particle(or bob) moves. The force in this case will not be central, but is constant in the vertical direction.