Snell's law example 2 | Geometric optics | Physics | Khan Academy | Summary and Q&A

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December 9, 2010
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Snell's law example 2 | Geometric optics | Physics | Khan Academy

TL;DR

This video explains how to calculate the distance traveled by a laser pointer in water using Snell's law and trigonometry.

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Q: What is the purpose of using Snell's law in this example?

Snell's law is used to determine the angles involved in the refraction of light as it passes from air to water, which helps calculate the distance traveled by the laser pointer.

Q: How is the distance along the surface of the water calculated?

The distance along the surface is calculated using the Pythagorean theorem, considering the height of the laser pointer above the water and the horizontal distance it travels to touch the water's surface.

Q: How is the angle of refraction determined?

The angle of refraction (theta 2) is calculated by finding the sine of theta 1, which is obtained by dividing the horizontal distance traveled by the laser pointer by the distance to the water's surface. The resulting value is then used in Snell's law to find theta 2.

Q: What is the final calculated distance for the laser pointer?

The final distance is calculated by adding the distance along the surface of the water (x), the incremental distance (y), and the depth of the pool (3 meters). The result is approximately 11.18 meters.

Summary & Key Takeaways

• The video demonstrates a more complex example of using Snell's law to calculate the distance a laser pointer travels in water.

• The process involves determining the distance along the surface of the water and the incremental distance from the surface to the bottom of the pool.

• Trigonometry is used to calculate the angles involved, allowing for the final distance to be calculated.