LIGHT

Hello fellow bloggers, my first post!

Light Diffraction Experiment:

The aim of our past experiment was to compare the spectrum of an energy-saving light bulb with that of a normal tungsten light bulb.The first time we attempted this experiment we came across some difficulty when trying to actually see the different orders, or groups of diffraction patterns that were visible to our eyes. However, after some useful instructions from classmates, we tried it again. This time we got much clearer results. After setting up our “lab,” we first tested out the tungsten light bulb. With this light bulb we were able to see two distinct orders of diffraction pattern. The observed rectangular areas of visible light behind the diffraction grating had three distinct colors—blue on the far right, green in the middle, and red on the left. In this case, the colors all blended together in a continuous fashion.

Order, n	Angle of diffraction	Uncertainty	Sin On	Uncertainty in sin On
Blue Spectral Line
1	53	1	0.799	0.017
2	57	1	0.839	0.017
Green Spectral Line
1	50	1	0.766	0.017
2	55	1	0.819	0.017
Red Spectral Line
1	47	1	0.731	0.017
2	53	1	0.799	0.017

Using the equation: wavelength=d x gradient we got the following values for wavelengths using the tungsten light bulb: blue= 400 nm, green=530 nm, and red=680 nm.

We then exchanged the normal tungsten light bulb out for the energy-saving light bulb. Using this light bulb we again only observed two different orders. However, in contrast to the normal light bulb, in these orders of lights the colors did not blend together continuously, rather they were discrete. This could possibly have something to do with how it saves energy, with the spectral lines representing that it only emits certain energies, whereas the normal lightbulb emitted wavelengths of all energies. We recorded and calculated the following values:

Order, n	Angle of diffraction	Uncertainty	Sin On	Uncertainty in sin On
Blue Spectral Line
1	32	1	0.530	0.017
2	35	1	0.574	0.017
Green Spectral Line
1	34	1	0.599	0.017
2	38	1	0.616	0.017
Red Spectral Line
1	36	1	0.588	0.017
2	41	1	0.656	0.017

Calculating the wavelengths, we got measurements of 440 nm for blue, 570 for green, and 680 for red. These were similar to the numbers we got when using the normal bulb, which makes sense because wavelengths of light for each color should not differ. These values are also relatively close to the actual values for the wavelengths of light for red, blue, and green.

When performing this experiment, a number of uncertainties arose. To take the measurements of the angles, the numbers were also a result from which angle we looked at the diffraction grating, so it was important to take measurements from the same viewing angle. Also, a very small error in measurements could result in a much larger difference in sin values and therefore wavelength measurements.