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Course: MCAT > Unit 3

Lesson 1: Foundation 4: Physical and chemical principles

Eye disease and contact lenses


Punctate keratitis is an eye disease that results in abrasions on the epithelial cornea. One of the leading causes of the disease is the overuse of contact lenses. The cornea requires exposure to oxygen in order to maintain a healthy exterior. Although it typically gets this oxygen from the air surrounding the eye, contact lenses may prevent this interaction from occurring to its desired potential.
A research team is investigating the optical properties of four new types of clear plastic to be used in prescription “soft” contact lenses. It is hypothesized that increasing the breathability of the lenses will allow oxygen to interact with the cornea through the lenses, circumnavigating one of the major issues associated with contacts. To investigate the refractive capabilities of the different types of plastic the team conducted an experiment by firing a red ray of light toward each type of plastic. The incoming angle θ was measured from the surface of the plastic and the outgoing angle φ was measured with respect to the dotted line shown below.
The data found in the experiment is shown in the following chart.
Type of Plasticθφ
Plastic 13043
Plastic 24831
Plastic 33437
Plastic 42562
What is the index of refraction of the red light in plastic 1?
Choose 1 answer: