Lesson: Dispersion

In this lesson, we will learn how to calculate the effect of variation of the refractive index of substances on the wavelength of the light that they refract.

Sample Question Videos

  • 08:35

Worksheet: 7 Questions • 1 Video

Q1:

A light ray, ray 1, of wavelength 660 nm and a light ray, ray 2, of wavelength 410 nm are incident on an interface of air and fused quartz. A light ray, ray 3, of wavelength 580 nm and a light ray, ray 4, of wavelength 470 nm are incident on an interface of air and diamond. The difference in speed between ray 1 and ray 2 is compared to that between ray 3 and ray 4. When comparing the pairs of rays, use a value of 1.455 for the refractive index of 660 nm light in fused quartz and a value of 1.468 for the refractive index of 410 nm light in fused quartz. Use a value of 2.417 for the refractive index of 580 nm light in diamond and a value of 2.444 for the refractive index of 470 nm light in diamond. Find the ratio of the difference between the speeds of ray 1 and ray 2 to that between ray 3 and ray 4.

Q2:

Light of wavelength 610 nm is incident on the interior surface of a diamond with a refractive index of 2.415 for that wavelength. Light of wavelength 470 nm is also propagating within the diamond and the refractive index of the diamond for this light is 2.444. The diamond is surrounded by air. What is the difference between the critical angle for the 610 nm wavelength light and the critical angle for the 470 nm wavelength light?

Q3:

A two-colored beam of light consisting of wavelengths of 610 nm and 410 nm propagates through quartz, with the two colors propagating parallel to each other. The beam is incident on a plane interface at an angle of 4 0 to the interface’s normal, where water is present on the other side of the interface. Find the difference in the angle from the interface’s normal of the two wavelengths when they propagate in water. Use a value of 1.456 for the refractive index of 610 nm wavelength light in quartz and use a value of 1.332 for the refractive index of 610 nm wavelength light in water. Use a value of 1.468 for the refractive index of 410 nm wavelength light in quartz and use a value of 1.342 for the refractive index of 410 nm wavelength light in water.

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