Experiment 8: Light and Color

Newton believed that light, in its purest form, was white. He also believed that refractive materials caused white light to create various colors. Newton demonstrated that refractive materials separated various colors, which are the constituents of white light. 

Procedure and Questions
-Rotate the Ray Table and observe color separation at large angles. 

Do your observations support Newton's theory? Explain.
Yes. The first setup demonstrated how a refractive material, a prism, separated light. This separation of light was visible on the viewing screen when we observed a variety of colors.

-Place the cylindrical lens so the three central rays (red, green, and blue) intersect at the same point. Observe the colors mix.

What color of light results when red, green, and blue light are mixed? How does this support Newton's theory?
White light is created when the rays are mixed. This explains that various colors make up white light. When the red, green, and blue light intersected on the viewing screen, we noticed white light as the product.

-Observe the light rays that are transmitted and reflected from the green filter.

What color are the transmitted rays? What color are the reflected rays?
The transmitted rays are green and the reflected rays are white.

-Place the red filter so light passes first through the green filter and then the red filter.

What color are the reflected rays now? Which rays are reflected from the front surface of the green filter, and which are  reflected from the front surface of the red filter?
The reflected rays are white. The rays reflected from the surface of the green filter are white. The rays reflected from the red filter are green.

-Place the blue filter over the light source so the incident rays are blue. Let these rays pass through the green filter only.

What color are the reflected rays now?
The reflected rays are blue.

Based on your observations, what makes the green filter appear green?
The green filter transmits green light and absorbs all other colors. When we look at the light created by the green filter, the light is green because the filter only transmits green light. However, if we look at the light reflected by the green filter, we observe white light because no light has been filtered. This is why we observed green light as the reflection from the red filter and the transmission from the green filter. 

Theory and Conclusion
Newton's experiment with two prisms proved that prisms did not add color to light. Rather, prisms could separate white light into various colors and combine the various colors back into white light.

The prism, the refractive material, separated light due to dispersion. As light passes from air to the prism, the light bends due to refraction. The degree of refraction depends on the wavelength of the rays. The constituents of the white light refract differently, which results in the color separation of white light.