Saved Bookmarks
| 1. |
Plane-polarized light of wavelength 589nm propagates along the axis of a concentration 500 g//l. Viewing from the side, one can see a system of helical fringes, with 50 cm between neighbouring dark fringes along the axis. Explain the emergence of the fringes and determine the specific rotation consatnt of the solution. |
|
Answer» Solution :Two effects are involved here : rotation of PLANE of POLARIZATION by sugar solution and the effect of that rotation on the scattering of light in the transverse DIRECTION. The latter is shown in the figure given below. It is easy to see from the figure that there will no scattering of light in this transverse direction if the incident light has its electric vector parallel to the line of sight. In such a situation, we expect fringes to occur in the given experiment. From the given data see that in a disatnce of `150 cm`, the rotation of plane of polarization must be `180^(@)`. Thus the specific rotation constant of suger `= ("rotation constant")/("CONCENTRATION")` `= (180//50)/(500(g)/(l))ANG//deg//cm = (180)/(5.0dm xx (.500 gm//c c))` `= 72^(@) ang deg// (dm gm//c c) (1dm = 10 cm)` 
|
|