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If the plane polarized light is passed through a plate of quartz or turpentine oil or the solution of sugar (taken in a glass tube) it is found that in the light the comes out, the plane of the polarized light gets rotated. The substances like quartz, sugar etc. Which rotate the plane of the polarized light are called optically active substances and the property of a substance to rotate the plane of the polarized light is called optical activity. The substances which rotate the plane of the polarized lift to the right are called dextero-rotatory (Latin: Dexter=right) and those which rotate the plane of the polarized light to the left are called laevo-rotatory (Latin: leaves=leafy). The method of observing the rotation of the plane of the polarized light is based upon the following principle: If the plane polarized light is passed thought another Nicola prism which and ‘brightness’ is observed thought the eye. On the other hand if the second Nicola prism is placed with its axis at rite annals tot hat of the first prism (called crossed position), the light is completely cut off and field of view in the eye piece is ‘dark’. At all other position, the brightness is less but there may but be complete darkness. It observed Principle of observing the rotation of the plane of polarized light that if the two Nicola prisms are set at the ‘crossed’ Position so that the field of view is completely dark and then the optically active substance is placed between the two prisms, the field of view becomes somewhat bright. The second prism has to be rotated through certain angle about the line of propagation of light to complete darkness again. This clearly shows that after passing through the optically active substance he plane of the polarized light has been rotated. The degree of rotation depends upon the rotation required to be given to the second Nicola prism to get the darkness again. Thus prism analyses the light and is called analyzer. For more help in Optical Activity click the button below to submit your homework assignment
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Škola Jeste li znali da na zaslonu kalkulatora ili digitalni sat je polarizatora? Napravite eksperiment u nastavku za vas promatrati polarizirane svjetlosti. Postavite leću polaroid naočale okrenute prema ostalim polaroid naočale leće, tako da objektiv je dva okrenuti jedni prema drugima. U ovom slučaju, su polarizacijski osi leće podudaraju, a svjetlost putuje normalno. Zatim okretati jedan od leće u odnosu na druge 90. i promatrati da se u tom slučaju nema svjetlost prolazi kroz leću. Zašto? Predložiti objašnjenje za ono što se dogodilo. Kako saznati je li molekula odstupa od ravnine polariziranog svjetla? Što je to? Napomena izgled jednog polarimeter (uređaji za mjerenje učinka koje polarizirano svjetlo pati u organskim spojevima). Može se dogoditi u sljedeće tri situacije polarimeter: Polarizirana svjetlost prolazi kroz uzorak u epruvetu i rotira u ravnini okrenuta udesno nego prije. U ovom slučaju, uzorak je optički aktivan, pozvao R (latinski rectus = pravo), jer su polarizirane svjetlosti zakrenuti za pravo, smjeru kazaljke na satu (+). Polarizirano svjetlo prolazi kroz uzorak u epruvetu i počne okretati u ravnini rotirati kako bi lijevo nego prije. U ovom slučaju, uzorak je optički aktivan, zove S (latinski zlokobno = lijevo), jer upletena polarizirano svjetlo na lijevoj strani, suprotnom smjeru (-). Polarizirano svjetlo prolazi kroz uzorak cijevi i drži vibrira na istoj ravnini. U ovom slučaju, uzorak nije imala aktivnost protiv svjetlosti, ili je optički neaktivni racemične poziv (jednaka mješavina R i S izomera). sintetske kemije