Question

Analytical Chemistry Tutorial: Introduction to Spectroscopy

Answer 1

if people could stop interrupting my tutorials before they're done that would be great

Answer 2

\({\bf{Vocabulary:}}\)
- spectroscopy: interaction of radiation and matter

- spectrometry: measurement of radiation w/ transducer or similar device

- diffraction: process by which a parallel beam of tradiation is ben as it crosses/passes through an opening

- coherent radiation: multiple sources of tradiation w/ the same frequency, and same phase relationship (ex: they are always either in phase or perfectly out of phase)

- refraction: change in the direction of radiation when passing through diff. media

- refractive index: n = c/v where n is the index, c is the speed of light, v is the speed of the radiation in that particular material. refractive index arises b/c radiation is slowed down in any medium, compared to the vacuum. the exact reason is difficult to explain but it has to do with how the radiation and physical medium interact (polarization)

- dispersion: the variation in refractive index w/ wavelength and frequency
> normal dispersion: refractive index increases gradually w/ frequency

- stopping voltage (from the photoelectric effect): voltage at which the photocurrent is 0, independent of intensity

KEm = hv - w
where KEm is the kinetic energy of the ejected electron, hv is the energy of the incident beam, and w is the work function (minimum binding energy of the electron in the metal)

- radiation from electric/thermal excitation is usu a result from vibrational energy level transitions

E = Eelectronic + Evibrational + Erotational

- nonradiative radiation: loss of energy in small steps, in which the lost energy is converted into KE through molecular collisions

- transmittance: T = P/P0 where P is the power of the beam after passing through the medium, and P0 is the original power

- absorbance: log(T)

- Beer's Law: epsilon * b * C where epsilon is the molar absorptivity, b is path length, C is concentration

Answer 3

\({\bf{Mathematical~Descriptions:}}\)
- Snell's law: gives the angle of incidence vs angle of refraction when radiation crosses into a diff. medium. remember that the angle is with reference to the normal.



- Young's double slit experiment


- velocity of a wave = frequency * wavelength
- y = Asin(ω*t + ф) where A is the amplitude, omega is the angular velocity, phi is the phase angle
if the phi diff. between two angles is 0, 360 degrees, etc. the waves are considered constructive, and if the diff is 180 + (360)n degrees, considered destructive

Answer 4

Source material is Chapter 6 of Principals of Instrumental Analysis, 6th edition by Skoog, Douglas A., Holler, James F., Crouch, Stanley R.