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The answer is (E) The light bulb produces unpolarized light, in which electric ﬁeld vibrations are
elgualhur probable in all directions perpendicular to the direction of propagation. The ﬁrst polarizer has a horizontal transmission axis, so it will ﬁlter out all but the
horizontal components of electric ﬁeld vibrations, producing light that is polarized
in the horizontal plane. The second polarizer has a vertical transmission axis, so
it ﬁlters out all but the vertical electric ﬁeld vibrations. The combination of two crossed polarizers is to completely absorb the light. However, if an optically active substance is interposed, it will rotate the hori- zontally polarized light emerging from the ﬁrst polarizer that passes through it.
Therefore, this light will have some vertical component to its electic ﬁeld vibrations
when it reaches the second polarizer. For this reason a portion of the light that
passes through the sample will be able to make it through the second polal'lzer.
The amount of brightness depends on the degree of optical rotation that occured
in the substance. OPTICAL ACTWIT'I", THE AEILIT'I" OF A SUBSTANCE TCI RﬂTATE THE PLANE CIF FDLARIIED ”El-IT, iS A
IIIII'EIT'I“lin'1P'l'Jl'liTiill‘il'l''|="|;|'PIC IH ORGANIC l:HEI'lI'IlSTII'l"A.l"-l3|I BIOCHEMISTRY. thlSTBIClCHEil-lICAL SUBSTANCES ARE OPTIC-ALB“ ACTIVE.
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- Spring '11