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Investigation 4 – PreLab









Optical engineers work in all areas of optics, using different techniques to design lasers, build telescopes, create fiber optics communication systems, and much more.


This Investigation is designed to help you to answer the following Focus Question:

  • How does a change in mediums affect the wavelength of light? 

Note: This question is located in your SDR at the beginning and end of the Investigation.



As a class, read the Background(s) in the Investigation. When finished, discuss the following concepts as a class:

  • The refraction of light occurs whenever light travels from one medium to another.
  • Because light waves travel at different speeds through different mediums, the light waves are bent as they move from one medium to another. For example, light travels at 290,000,000 m/s in the air but slows down to 225, 000,000 m/s in water. The lightwave slows as it enters the water, and bends or refracts. As a result, if we were to view an object at the bottom of a pool or lake through the water, it would appear different than if it were viewed in air, outside of the water.
  • The angle at which the light wave enters the water is called the angle of incidence.
  • The angle at which the light wave is refracted in the water is called the angle of refraction.
  • Different transparent mediums or substances refract or bend light to different degrees.
  • A measure of the degree to which a medium refracts light is indicated by a value called the index of refraction.
  • The index of refraction of air is 1.00.



The following list includes Key Terms that are introduced in the Investigation Background(s). They should be used, as appropriate, by teachers and students during everyday classroom discourse.

  • refraction
  • index of refraction

Note: Definitions of these terms can be found on the Introduction page to the CELL.

Note: Additional words may be bolded within the Background(s). These words are not Key Terms and are strictly emphasized for exposure at this time.


  • Review the three ways in which light can interact with a medium – transmission, absorption, and reflection. How does each of these relate to the perception of color?
  • Summarize how you have investigated the behavior of light thus far.
  • You will now investigate a fourth way in which light can interact with a medium, refraction.
  • Reflect on what they have learned about refraction thus far then complete the Apply section in your SDR. 
  • Can you think of an everyday life application of refraction?
  • What might you observe as an example of refraction?
  • Play the video below. Remember to follow along with your SDR and make any notes that you think might be helpful.
  • After the video, divide into your lab groups to discuss strategy for the lab. For example, you may assign certain group members to perform specific functions during the lab.

Note: The purpose of the video is to allow you to anticipate the laboratory experience you will soon encounter. You should leave this PreLab session with a firm idea of what to expect and how to perform in the lab.

Note: Homework is posted below the video.


You should review the Investigation and video in preparation for the Lab.