11 August, 2010

Photos of Light spectrum through diffraction grating

In addition to my Polarising film set up I am trying to create a set up to show how light is split when passing through diffraction grating. So I picked up a grain of wheat bulb and set about trying to work out how would be best to show this.
Unlike my polarising film photos the set up was not already created, so these photos are from my first round of trials and there will be more when I have managed to incorporate the modifications that showed to be necessary from this round.

I did initially try a round of photos with an E10 bulb and a white background but this was too large a light source and the white background meant that it washed the colour out of the spectrum and provided problems when trying to clean up the images.

So my first modifications resulted in using a black table as a background and taking the photos in the dark (except for the bulb) to reduce the amount of background light, and using a grain of wheat bulb since this would produce a much smaller light source.
I am yet to decide if taking photos in a dark room is a good idea or not since when the light source is in the photo it 'burns out' due to being so much brighter than the surrounding image.

This image shows how bright the light is but also shows the colours produced quite well.

This was only the second photo I took with this set-up and here I will have to apologise for the quality of the photos since it was only a trial they are only taken using my iPhone camera.

This shows how the main part of the spectrum is 'burnt out' since it it much brighter but it also shows the range of colours that the light produces and shows the start of a second 'tail' out side of the initial spectrum. Here the light source is to the left of the image.

Another problem that shows up on some of these images in that the Diffraction Grating that I used was just held by me in one hand so it had a tendency to bend resulting in bent spectrum lines this will be rectified in future photography sessions by mounting the diffraction grating before using it. I will also mount the camera since these images are taken in the dark resulting in a long exposure time so to create a higher quality photograph mounting the camera would reduce the blur created by movement of the camera.

The first set of images were taken with either 500 or 1000 lines/mm Single Axis Diffraction grating but I also had 532 lines/mm Twin-Axis Diffraction Grating to play about with and this produced some much more interesting images

Here the spectrum is split as
it was before but due to the diffraction grating having two axis the light is split in many directions producing this interesting star effect.

To view more of the initial photos see them here

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