MadSci Network: Physics |
Different wavelengths/frequencies refract differently because the speed of light in the material (and thus the index of refraction) is a function of frequency. For most materials, the index of refraction is higher for purple light than for red light. Thus shorter wavelengths usually refract more, when dealing with visible light. At other frequencies this is not always the case. For example, when seen in far-infrared light, water has an index of refraction which gets bigger at lower frequencies. Thus,very low frequency infrared light refracting through water will bend more towards the normal than high frequency infrared light. At frequencies of visible light, water's index of refraction is slightly higher for higher frequencies, so blue or purple light refracts more than red light. How the index varies with frequency just depends on the material involved, and on how its molecules vibrate in response to different frequencies of light. High frequencies try to vibrate the molecules rapidly, and low frequencies try to vibrate them slowly. The response is different, so the index of refraction is different.
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