OpticsLesson 1 of 2 in the course The Nature of Light

Wavelength-Dependent Dispersion, Refraction, and Rainbows

5 flashcards · 5 quiz questions · 5 match pairs · 4 fill-in sentences · English

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Summary

Dispersion explains how waves that contain different wavelengths or frequencies can spread apart as they travel. It helps us understand why white sunlight can form a rainbow and why the behavior of waves can reveal information about the materials they pass through.

Visible light is electromagnetic radiation that our eyes can detect. Different wavelengths are perceived as different colors. Red light has a longer wavelength than violet light; in the visible spectrum, the approximate values range from about 660 nm for red to about 410 nm for violet.

All flashcards

Dispersion
The spreading of a wave according to wavelength; for white light, it separates component wavelengths.
Monochromatic light
Light dominated by a single wavelength.
Wavelength and refractive index
In many transparent materials, shorter wavelengths have a higher refractive index than longer wavelengths.
Snell's law
The relation between incidence and refraction angles is n1sin⁡θ1=n2sin⁡θ2n_1\sin\theta_1=n_2\sin\theta_2.
Primary rainbow
A rainbow formed by two refractions and one internal reflection within water droplets.

Quiz questions

  1. In many transparent materials, how does refractive index vary as wavelength decreases?Answer: It increases.
  2. What sequence of interactions produces a primary rainbow in a water droplet?Answer: Refraction on entry, one internal reflection, then refraction on exit.
  3. How does the color order of a secondary rainbow compare with that of a primary rainbow?Answer: The color order is reversed.
  4. Why can wavelength dispersion make optical-fiber messages harder to distinguish?Answer: Different wavelength components of a pulse can spread it in time until neighboring pulses overlap.
  5. In which direction should an observer look to see a rainbow caused by sunlight?Answer: Away from the Sun.

Based on University Physics Volume 3 by Samuel J. Ling, Jeff Sanny, William Moebs (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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