Optical spectrometer experiment

[LoD]

Hi,
I need to do an experiment to calculate Planck's constant from LEDs. Basically what I'm intending to do is a fairly simple variable dc supply->voltmeter->LED->spectrometer->diffraction grating->my eye type setup. I know how to do that, but the trouble is I'll need to track down a diffraction grating. What I'd like to know is, would it be possible to use a triangular prism instead and work out the wavelength using refraction? In theory it should, but would it in practice?
Thanks

 

[andrevdh]

Assuming that you know the energy gap $E_g$ of the LED you can construct a calibration curve with the prism by plotting the minimum deviation angles, measured with the spectroscope, for various spectral lines, against their wavelengths. Use this curve to determine the wavelenght of the LED.

 

[kyle8921]

Hello,

Thank you for sharing your experiment idea. It sounds like you have a good understanding of the setup and process for measuring Planck's constant using LEDs. In regards to using a triangular prism instead of a diffraction grating, it is possible in theory to calculate the wavelength using refraction. However, in practice, it may not be as accurate or precise as using a diffraction grating. This is because a diffraction grating is specifically designed for separating and measuring wavelengths, while a triangular prism may introduce more sources of error. Additionally, the dispersion of light through a prism can vary depending on the material and shape of the prism, making it difficult to accurately determine the wavelength. I would recommend trying to obtain a diffraction grating for the most accurate and reliable results. Best of luck with your experiment!