PHO 101 Photonics Concepts
Three Rivers Community College ONLINE
Home Lab #1
CAUTION! Do not look into the laser cavity, or at any reflections of the laser from shiny surfaces. Do not look at the sun!
Purpose: To examine the color (wavelength) composition of several light sources.
Equipment:
Procedure: The diffraction grating in your optics kit can give a qualitative picture of the wavelengths (colors) that are radiated by a source of light. To get the clearest spectra, you first need to construct a spectroscope.
1. Making the spectroscope:
Figure 1
2. Observing sources
How to view the spectra: Look through the diffraction grating with the pinhole pointed toward the source. You may need to have the hole close to the source so light from windows and lamps dont enter the spectroscope as well. You will see a bright spot in the center (which will have the same color as the source itself). On either side, you will see one (or more) "spectra"- a full rainbow for a source like a light bulb and individual lines for sources like street lights or energy saving fluorescent bulbs. Focus on one of these spectra, which will include some or all of the colors of the visible spectrum. For an example of what you will see, look at the figures below.
Find at least five different sources of light in and out of your home. (Hint: anything that glows is fair game- e.g., stove unit, candle flame, street lights, etc) If you can find a colored light (such as a green night light or holiday bulb) that would be an excellent addition.
If you have a laser pointer, you can include it as one of your sources. However, DO NOT look directly into the laser with your spectrometer. Shine the laser on a piece of white paper and look at the spot on the paper. You can view the spectrum of sunlight the same way, by looking at sunlight reflected from white paper.
Lab Report: Find the data table for this lab in the lab folder, or make one of your own. For each source, list the type of light and a description of the spectrum you see through the spectrometer- what colors are present and which of the colors are brighter/dimmer. Then answer the following questions:
Questions:
To see additional spectra, plus photos of the "homemade spectroscope" used in this lab, visit http://www.lasertechonline.org/optics/spectrascope.html The photos on this web site were taken with a variety of gratings that separated the spectra by different amounts. Hopefully, the grating included in your optics kit will show only one spectrum on either side of the central image of the source.