Significance This is the index of refraction for water, and Snell could have determined it by measuring the angles and performing this calculation. He would then have found 1. Today, we can verify that the index of refraction is related to the speed of light in a medium by measuring that speed directly.
Explore bending of light between two media with different indices of refraction. Use the protractor tool to measure the angles and see if you can recreate the configuration in Figure. Also by measurement, confirm that the angle of reflection equals the angle of incidence. A Larger Change in Direction Suppose that in a situation like that in Figure , light goes from air to diamond and that the incident angle is.
Calculate the angle of refraction in the diamond. Strategy Again, the index of refraction for air is taken to be , and we are given. We can look up the index of refraction for diamond in Figure , finding.
Significance For the same angle of incidence, the angle of refraction in diamond is significantly smaller than in water rather than —see Figure.
This means there is a larger change in direction in diamond. The cause of a large change in direction is a large change in the index of refraction or speed. In general, the larger the change in speed, the greater the effect on the direction of the ray. Check Your Understanding In Figure , the solid with the next highest index of refraction after diamond is zircon. If the diamond in Figure were replaced with a piece of zircon, what would be the new angle of refraction? Diffusion by reflection from a rough surface is described in this chapter.
Light can also be diffused by refraction. Describe how this occurs in a specific situation, such as light interacting with crushed ice. Will light change direction toward or away from the perpendicular when it goes from air to water? Water to glass? Glass to air? Explain why an object in water always appears to be at a depth shallower than it actually is? Justify your explanation with a ray diagram showing the path of rays from the feet to the eye of an observer who is out of the water.
Early scientists realized that the ratio between the angle at which the light crosses the media interface and the angle produced after refraction is a very precise characteristic of the material producing the refraction effect. A number of phenomena that result from light refraction are often observed in everyday life, including the illusion, created by refraction effects, of the actual depth of a fish in shallow water when observed from the bank of a lake or pond.
When we peer through the water to observe fish swimming around the pond, they appear to be much closer to the surface than they really are. On the other hand, from the fish's point of view, the world appears distorted and compressed above the water due to virtual images created by refraction of reflected and transmitted light reaching the eyes of the fish. In fact, due to refraction, a fisherman on the bank appears to be farther away from the fish from the fish's viewpoint than he or she really is.
Matt Parry-Hill and Michael W. Observing Objects in Water. Light coming from the fish refracts changes direction when it hits the surface. A person above the water sees the apparent position of the fish closer to the surface than the real position of the fish. In this activity, students aim spears at a model of a fish in a container of water. When they move their spears towards the fish, they miss!
This activity investigates refraction. By the end of If there is no light, there is no sight — explore our resources and learn more about the basics of light, how we see and how we perceive the world around us.
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