Physics Definitions

[Nobody]

Light Emission

Excitation: the process of boosting electrons in an atom or molecule from a lower to a higher energy level.

Emission Spectrum: the distribution of wavelengths in the light from a luminous source.

Spectroscope: an optical instrument, separates light into its constituent frequencies in the form of spectral lines

Incandescence: the state of glowing while at a high temperature, caused by electrons in vibration atoms and molecules that are shaken in and out of their stable energy levels, emitting radiant energy in the process. The peak frequency of radiant energy is proportional to the absolute temperature of a heated substance; f ~ t

Absorption Spectrum: a continuous spectrum, like that of white light, interrupted by dark lines or bands that result from the absorption of certain frequencies of light by a substance through which the radiant energy passes.

Fluorescence: the property of absorbing radiant energy of one frequency and re-emitting radiant energy of lower frequency. Part of the absorbed radiant energy goes into heat and the other part into excitation; hence the emitted radiant energy has a lower energy and therefore a lower frequency than the absorbed radiant energy.

Phosphorescence: a type of light emission that is the same as fluorescence except for a delay between excitation and de-excitation, which provides an afterglow. The delay is caused by atoms being excited to energy levels that do not decay rapidly. The afterglow may last from fractions of a second to hours, or even days, depending on the type of material, temperature, and other factors.

Laser (light amp. by stimulated emission of radiation): an optical instrument that produces a beam of coherent monochromatic light.

Coherent light: all the waves are identical and in phase.

Notes:
l=c/f

The temperature of incandescent bodies, whether they be stars or blast-furnace interiors, can be determined by measuring the peak frequency of radiant energy they emit.

Incoherent white light contains waves of many frequency (and wavelengths) that are out of phase with one another

Light of a single frequency and wavelength is still out of phase

[Nobody]

Light Quanta

When the energy of a photon is divided by its frequency, the single number that results is the proportionality constant, called Planck’s constant, h (6.6 x 10-34 joule- sec)

Observations contrary to the wave picture for the analysis of photoelectricity:

1] the time lag between turning on the light and the ejection of the first electrons was not affected by the brightness or frequency of the light. 2] the effect was easy to observe with violet or ultraviolet light, but not with red light. 3] the rate at which electrons were ejected was proportional to the brightness of the light. 4] the maximum energy of the ejected electrons was not affected by the brightness of the light, but there were indications that the energy did depend on the frequency of the light.

-one photon is completely absorbed by each electron ejected from the metal.(all or nothing)

-the energy of each photon is proportional to the frequency of light, while the number of photons has to do with its brightness.

-light travels as a wave and hits as a stream of photons

The act of observing something as tiny as an electron produces a considerable uncertainty in either its position or its motion.

Summary of terms:

Complementarity: (Bohr) the principle that wave and particle models of either matter or radiation complement each other and when combined provide a fuller description of either one.

[Nobody]

The Atom and the Quantum

The electron doesn’t radiate light while it accelerates around the nucleus in a single orbit, but that radiation of light takes place only when the electron jumps orbit from a higher energy level to a lower energy level.

Color depends on the (distance of) jump. Bohr’s views explained the regularities being found in atomic spectra.

Ritz combination principle: the theory that the spectral lines of the elements have frequencies that are either the sums or the differences of the frequencies of two other lines.

de Broglie matter waves: the associated wave properties of all particles of matter. The wavelength of a particle wave is related to its momentum and Planck’s constant, l=h/momentum

Shrodinger’s wave equation: the fundamental equation of quantum mechanics, which interprets the wave nature of material particles in terms of probability wave amplitudes.

Correspondence principle: the rule that a new theory is valid provided that, when it overlaps with the old, it agrees with the verified results of the old theory.

That's all! 

[Saladin]

Very comprehensive. Good work man!

[Arthur Bon Zavi]

quickk notes....refrence...thanx man

[Master_Key]

i uploaded quick refrence many times