CHEM1101 Lecture Notes - Lecture 13: Atomic Spectroscopy, Microscopy, Transparency And Translucency
15 May 2018
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Lecture 13 – Atomic spectroscopy and Molecular spectroscopy
Spectroscopy
• The study of the interaction of matter with electromagnetic radiation.
• There are many different forms of spectroscopy.
• The type of electromagnetic radiation used, instrumentation, and sample preparation determines
the information that will be obtained
o E.g. MRI, Light microscopy, X- ray imaging
Color
• White – combination of all colors, absorb no visible light
• Black – absorb all visible light shone on them
• Colors are due to particular wavelengths of light they absorb
• A solid that absorbs red light and reflects all the other colours will appear
green. A solid that absorbs green light is perceived by us as a red colour.
• A Newton’s colour wheel lets us predict the colour that will be observed
Terms to describe color
• Transparent materials allow all light to pass through
o e.g. air, water, clear glass
• Translucent materials allow some light to pass through, and the rest is scattered
o e.g. frosted glass, some plastics, pearl)
• Opaque materials do not let any light pass through. Light is reflected or absorbed
o e.g. wood, stone, metals
• The designation of a material as coloured or colourless is separate from these terms.
o An opaque, colourless material will be white, while a transparent, colourless material will be
clear.
Atomic spectroscopy
• Each atom has different energy atomic orbitals, so distances and energy between atomic orbitals
are also different
• Flame test makes use of these differences
Li
Crimson
Rb
Red (reddish-violet)
Na
Yellow
Cs
Blue-violet
K
Lilac (purple)
Ca
Brick red
Sr
Red
Ba
Pale green
Cu
Blue-green
Pb
Greyish-white
Mg
No color
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Document Summary
Lecture 13 atomic spectroscopy and molecular spectroscopy. Spectroscopy: the study of the interaction of matter with electromagnetic radiation, there are many different forms of spectroscopy, the type of electromagnetic radiation used, instrumentation, and sample preparation determines the information that will be obtained, e. g. A solid that absorbs green light is perceived by us as a red colour: a newton"s colour wheel lets us predict the colour that will be observed. Light is reflected or absorbed: e. g. wood, stone, metals, the designation of a material as coloured or colourless is separate from these terms, an opaque, colourless material will be white, while a transparent, colourless material will be clear. Atomic spectroscopy: each atom has different energy atomic orbitals, so distances and energy between atomic orbitals are also different, flame test makes use of these differences. In 1885 balmer showed that the visible line spectra follow the equation: uv and ir spectral lines are defined by similar equations.
