SPECTROSCOPY

Fascinating Light Fireworks  Various colors  Due to atomic spectra of various elements  Na (yellow), Sr (red), Ba (blue)  Light transmitted through space Aurora borealis or “Northern Lights”  Light transmitted through space london.co.uk/images/template _5_06.jpg 2

Spectroscopy  The science that deals with the interactions of electromagnetic radiation (EMR) or light with matter Electromagnetic radiation (EMR) - or simply light, is energy traveling through space. 3

Electric fieldMagnetic field Light = Electromagnetic Radiation magnetos/friends.html 5c0f8d193a_m.jpg 4

In vacuum, EM waves travel at a constant speed of 3.00 x 10 8 m/s 5

Image available at herschel.jpl.nasa.gov 6 High energy Low energy High frequency Low frequency Short wavelength Long wavelength

Visible light, the light that we see with our eyes, is only a small portion of the EM spectrum - Associated with rainbow colors 7

A Continuous Spectrum Image available at A prism can break white light up into the visible light spectrum, resulting into a continuous spectrum. Here the spectrum shows a smooth transition between colors (or wavelengths). Continuous spectrum 8

A Line Spectrum Image available at When a gaseous element is heated to its excited state, it emits light (wavelengths) in discrete patterns called a line spectrum 9

Fascinating Light Fireworks  Light transmitted through space  Basically show the emission spectra of various elements in firework mixture Image available at 10

Examples of everyday life spectroscopy (matter- light interaction) MatterLight (EMR)Effect SuntanUV lightTans or burns skin Chlorophyllvisible lightSynthesis of food Tuning circuitsradiowavesProduces sound 11

 The higher the absorbance (A), the higher is the amount or concentration of substances (ex. blue dye) in solution Amount of Light Absorbed Related to Concentration  We can use a spectrometer, measure absorbance and calculate the amount of blue dye in solution

Spectrometer image available at: NOTE: This process only works for colored solutions. A SPECTROMETER

 The higher the absorbance (A), the higher is the amount or concentration of substances (ex. blue dye) in solution Amount of Light Absorbed Related to Concentration  We can use a spectrometer, measure absorbance and calculate the amount of blue dye in solution  How exactly is absorbance related to concentration?

Use of Standards in Measurements How long is the object in this picture? What do we need to measure its length?

Use of Standards in Measurements The ruler is a standard used for measuring length. Blue dye standard solutions are used for measuring the amount of blue dye in commercial drinks.

How much blue dye is in Gatorade?  Use a spectrometer  Measure absorbance of light, A  Compare with A of known amounts or concentrations of blue dye (called blue dye standards)  Create a graph of A versus known amount of blue dye standards = Standard Curve  Using A of sample (ex. Gatorade) with unknown amount of blue dye, extrapolate to determine amount of blue dye in sample  Each blue dye standard has a fixed amount of blue dye  Much like each scale in a ruler --- has a fixed measurement)

Absorbance and concentrations of blue dye standards

Standard No. ppm (mg/L) concentration of standard solution Absorbance at 630 nm Sample 1?0.402 x ppm blue dye in sample A Sample

Percent (%) vs. Parts-per-million (ppm) Example%ppm Normal CO 2 level Permissible CO level Percent = parts per hundred (pph) Parts-per-million = one part in a million parts (ppm) Toxic gas; lethal level in ppm scale ppm = % x 10,000 or simply 21

Standard No. ppm (mg/L) concentration of standard solution Absorbance at 630 nm Sample 1?0.402 x ppm blue dye in sample A Sample