15A.2 Flashcards
what is plane-polarized light
monochromatic light that has oscillation in only one plan
what is unpolarized light
light that has oscillation in all planes at right angle to the direction of travel
what is optical activity
a substance that shows optical activity rotates the plane of polarization of a plane polarized light
what is a polarimeter
the apparatus used to measure the angle of rotation caused by a substance
what is a polariser
a material that converts polarized light into plane-polarized light for example polaroid
what is an analyser
it is a material that allows plane-polarized light to pass through
how does polarimeter work
monochromatic light is passed through the first polarizing filter which produces plane polarized light which is then passed through sample tube which contains a substance in solution, if the substances has optical activity (contains an enantiomers) then the plane-polarized light will be rotated and will no longer be vertical, then it will pass through another polarizing filter which is called the analyser which rotates to allow maximum light intensity the angle which the analyzer is rotated is how much the substance rotated the light.
if the rotation in the polarimeter is clockwise the substances can be described as
dextrorotatory
if the rotation in the polarimeter is anti-clockwise the substances can be described as
laevorotatory
if the rotation in the polarimeter is clockwise then the angle is
positive
if the rotation in the polarimeter is anti-clockwise then the angle is
negative
two enantiomers have the same physical property with one exception which is
they rotate the plane of polarization of plane-polarized light with the same angle but different direction
two enantiomers have the same chemical property with one exception which is
they way they react with enantiomer of other substances. this chemical property might be different to for each enantiomer
what is a racemic mixture
an equimolar mixture of two enantiomers that have no optical activity
why do racemic mixtures have no optical activity
because the effect from each enantiomer cancel out since they rotate in opposite direction
