A surface, or a line in a two-dimensional representation, joining points on a wave that are at the same phase.

State Huygens’s principle.

Every point on a wavefront acts as a source of forward-traveling wavelets. Their forward common tangent forms the new wavefront.

How does refractive index relate to light speed in a medium?

The speed is $v=c/n$, where $c$ is the speed of light in vacuum and $n$ is the refractive index.

What is Snell’s law?

$n_1\sin\theta_1=n_2\sin\theta_2$, with both angles measured from the normal.

The bending and spreading of a wave as it passes around an obstacle or through an opening.

OpticsLesson 1 of 1 in the course The Nature of Light

Huygens Wavefronts: Reflection, Refraction, and Diffraction

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

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Summary

This lesson introduces Huygens’s principle, a wave-based method for predicting how waves propagate. It also shows how the principle accounts for reflection from a mirror.

A wave has both a direction of travel and a repeating pattern of oscillation. For light, the electric and magnetic fields oscillate, but it is often more useful in wave optics to represent the wave by its wavefronts. A wavefront is a surface (or line in a two-dimensional drawing) joining points that are at the same stage of oscillation, such as points along a crest.

All flashcards

What is a wavefront?: A surface, or a line in a two-dimensional representation, joining points on a wave that are at the same phase.
State Huygens’s principle.: Every point on a wavefront acts as a source of forward-traveling wavelets. Their forward common tangent forms the new wavefront.
How does refractive index relate to light speed in a medium?: The speed is $v=c/n$ , where $c$ is the speed of light in vacuum and $n$ is the refractive index.
What is Snell’s law?: $n_1\sin\theta_1=n_2\sin\theta_2$ , with both angles measured from the normal.
What is diffraction?: The bending and spreading of a wave as it passes around an obstacle or through an opening.

Quiz questions

According to Huygens’s principle, what acts as a source of secondary wavelets?Answer: Every point on an existing wavefront.
In a Huygens construction, what represents the later wavefront?Answer: The forward common tangent to the wavelets.
A light ray strikes a plane mirror at an incidence angle of $35^\circ$ . What reflection angle is predicted?Answer: $35^\circ$ , measured from the normal.
What happens to light’s speed when it enters a medium with a higher refractive index?Answer: Its speed decreases.
Why does sound generally spread through a doorway more noticeably than visible light?Answer: Sound wavelengths are larger relative to the doorway.

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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