Prism Spectrometer

Shock Hazard: The power sources for the discharge tubes use a very high voltage to excite the tubes of gas. When changing the tubes from hydrogen to helium or mercury, make sure that the supply is turned off when removing or inserting a discharge tube.
Burn Hazard: When the discharge tubes are in use, a large amount of energy is being converted to heat and light. This means that the tubes heat up considerably when lit. Do not grasp them in the middle of the tube, this is its hottest point and you could burn your fingers. The wider sections of the tube at its ends will not be quite as hot and will be safer for you to hold when removing the tube from the power supply.

Make sure that the slit in the collimator is placed as close to the discharge tube as possible and that it is centered on the tube. This will assure that the spectral lines you study will be as bright as possible and will therefore be easier to study.
Some students may have trouble seeing the fainter spectral lines. This is especially true of the lines at in the violet portion of the spectrum. Not alleyes are sensitive to the same range of EM frequencies. Some people can see more easily in the red to near infra-red and others have an easier time seeing light in the violet to near ultra-violet part of the spectrum. There should be plenty lines visible to have the requisite ten points on the plot if you use some lines from each of the hydrogen, helium, and mercury spectra.
Find the angle of minimum deviation for EACH of the spectral lines. The different wavelengths will have different angles of minimum deviation because the index of refraction is different for each of the wavelengths. Make sure you know how to determine this angle of minimum deviation before taking data. Your first graph will be of wavelength versusminimum deviation angle.
Use equation 2 to find the index of refraction for each of the tenwavelengths you used. Make a second graph of index of refraction versuswavelength.
Extra Credit: Prove geometrically that the apex angle of the prism is exactly half of the angle between the two reflected rays in Procedure 5 and Figure 2.

Your results section should include the index of refraction for the sodiumyellow line found using equation 2 and that obtained from your graph. Alsoreport the percentage difference between the two values.
Does your graph of wavelength versus minimum deviation angle form a smoothcurve? Is the average slope of the graph positive or negative? Does thiscorespond to what you would expect from the theory you have learned? Why orwhy not?
Does your graph of index of refraction versus wavelength form a smoothcurve? Is the average slope of the graph positive or negative? Does thiscorespond to what you would expect from the theory you have learned? Why orwhy not? Compare your graph with the one in the Jones & Childers textbook,p769.