Hello,
I am having a probably very easy question concerning the grating period on a diffraction grating (blazed grating) but I just wanted to check if my considerations are correct.
According to the grating equation, an increase in the spacing between the slits decreases the diffraction angle. So when I have a constant angle of incidence and observation angle at which I can see for example green light (1. order) and I would then increase the spacing, would I then observe light with a longer wavelength than the green light from the same observation angle?
Thanks in advance for your help!
Cheers
Chiara
Yes, you are correct. As you might have noticed, the grating equation involves the ratio of the wavelength of incidence to the grating period. Keeping the wavelength constant, increasing the grating period decreases the diffraction angle. Notice how the same trend can be achieved by keeping the grating period constant and decreasing the wavelength instead. This means that a shorter wavelength of light perceives the grating to have a bigger period in comparison with its own small wavelength, thereby diffracts at a smaller angle. The longer wavelength of light similarly diffracts at a larger angle.
This animation might help you visualise it better: https://youtu.be/UFh7hkLeL10?t=830. I'd recommend watching the entire video if you're new to it.
That is true. Grating equation says sin(D)=lambda/d-sin(I), with d the grating line distance, I and D the incident and diffracted angles. To compensate a larger d it needs a larger wavelength also to result in the same ratio and diffracted angle.
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