Qualification > Sciences
Edexcel PHYSICS Doubts
Saladin:
--- Quote from: Austrakast on May 08, 2010, 04:05:09 pm ---here's a question i need help solving:
A student observes the diffraction of white light by holding a diffraction grating close to her eyes
a)draw a simple diagram to illustrate what the student observes
b) a tube of KMn04 solution is placed in front of white light source.Then the student views the filament through the solution with the grating close to her eyes. she notices that the blue, yellow and orange colors have vanished. Give an explanation.
Can you please help me asap? Thanks ! :)
--- End quote ---
(a) A variety of colours, like that of a rainbow, all mixed up in one place.
(b) The light will be polarised. This means that the vibrations that have caused the other different colours of light no longer vibrate due to this polarisation.
Darth Austrakast:
thanks
but i wrote exactly same for the last answer but still got wrong
but thanks a lot for confirming it :)
vanibharutham:
Maybe certain colours of the white light have been absorbed by the purple colour of potassium permanganate solution. I doubt that KMnO4 will be optically active... and thus will not polarize light... i know for sure that organic molecules like sucrose and glucose are optically active.. they demonstrate chilarity, but KMnO4 is ... ionic solution....
vanibharutham:
i got it!
absorption spectra
the KMnO4 solution must have electrons that get excited whenever there is blue, yellow or orange light.
The excited electrons return to ground state and reemit the light equally in all directions. To an observer with a diffraction grating it seems like there is no orange, yellow or blue because the intensity is soo less
Saladin:
--- Quote from: vanibharutham on May 12, 2010, 07:03:50 pm ---i got it!
absorption spectra
the KMnO4 solution must have electrons that get excited whenever there is blue, yellow or orange light.
The excited electrons return to ground state and reemit the light equally in all directions. To an observer with a diffraction grating it seems like there is no orange, yellow or blue because the intensity is soo less
--- End quote ---
It has to be optically active then, which it is not. I believe your first point was correct.
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