The Foundations of Chemistry

990 CHAPTER 25: Coordination Compounds

Sodium

lamp

Polarizing filter

Polarizing filter

oriented parallel

to first

Polarizing filter

oriented perpendicular

to first

No light is

transmitted

Undiminished

intensity

“Plane” of

polarized light

Monochromatic

light

Polarizing

filter

Light

source Sample

cell

Detector

Figure 25-4 Light from a lamp or from the sun consists of electromagnetic waves that

vibrate in all directions perpendicular to the direction of travel. Polarizing filters absorb all

waves except those that vibrate in a single plane. The third polarizing filter, with a plane of

polarization at right angles to the first, absorbs the polarized light completely.

Figure 25-5 The plane of polarization of plane-polarized light is rotated through an angle

( ) as it passes through an optically active medium. Species that rotate the plane to the right

(clockwise) are dextrorotatory, and those that rotate it to the left are levorotatory.