PHYS320 Lab 25 Light and Color

Experiment 1: Color Reflection

Experiment 2: Prisms


1. Which color refracted the most through the prism? Is the refractive index for a material higher or lower for smaller wavelengths of light? Use Figure 1 if you need help.

2. Complete the picture below to match the color pattern from your prism. As you can see, the light is refracted twice through two sides of the prism surface.

3. If the refractive index of your prism was higher, would you get a pattern that is wider or narrower? In other words, would the red and blue sections be farther apart or closer together?

Experiment 3: Reflection and Refraction

d = 18cm


1. Measure the distances marked by the segments AC and AB.

2.Use trigonometry to solve for your angle values θ1 and θ2 using the lengths above and the distance, d

3.Use Snell’s law to solve for the index of refraction of water. Remember that the index of refraction of air can be taken as 1.00.

4.How does your measured value compare to the accepted value of Table 1?What is the percent error?

5.What are some of the sources of error present that could have affected your result?

6.How did adding oil to the cell change the refraction of the beam? Does this indicate that the oil has a higher or lower refractive index than water?

Experiment 4: Diffraction Interference

DataPart 1

· Observations and drawing for the spectrum produced by the CD and flashlight:

· Observations and drawing for the spectrum produced by the CD and laser pointer:

Part 2

· Observations for the laser pointer shone through 1000 and 500 lines/mm diffraction gratings:

· Observations and drawing for the flashlight shone through the diffraction grating:


Calculate the wavelength of the laser light using the modified “grating equation” for d = 1/500 mm:

nλ = d (X/L)

Keep all calculations in millimeters (mm) until the end and then convert your answer to nanometers (1 nm = 10-6 mm). Remember that your measurements are to the first bright spot (what is the value for n?). Show all your work below:


1. Why did the spectra for the laser light and flashlight differ when reflected from the CD surface?

2.What was the result of shining the flashlight through the diffraction grating compared to the laser? Explain this difference.

3.Is the value you obtained for the wavelength of the laser light consistent with the range of wavelengths for the red light? Explain any sources of error that might have caused a large deviation.

4.You see a girl with a beautiful jeweled ring reflecting light brightly off her finger. If the reflected light appears purple and green on a piece of paper near her hand, what wavelengths of light do you suspect the jewel reflects?

5. A laser light was shone through a diffraction grating whose lines were 1/1000 mm apart. The distance was measured between the center spot and the first side spot and found to be 99 mm. The distance from the diffraction grating to the first side spot was found to be 154 mm. Calculate the wavelength of light in nm that the laser pointer was emitting.


PHYS320 Lab 25 Light and Color
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