State Huygens principle.

In an isotropic medium, what is the relationship between rays and wavefronts?

A wave travels at \(2.0\times10^8\,\mathrm{m\,s^{-1}}\). How far do Huygens wavelets expand in \(1.5\,\mathrm{ns}\)?

How does Huygens principle explain the law of reflection?

If light enters a slower medium, how does the Huygens construction predict the ray bends?

If light enters a faster medium, how does the ray bend according to the Huygens construction?

State Snell's law in speed form.

A wavefront enters a medium where its speed changes from \(3.0\times10^8\,\mathrm{m\,s^{-1}}\) to \(2.0\times10^8\,\mathrm{m\,s^{-1}}\). If \(\theta_1=45^\circ\), find \(\theta_2\).

Use Huygens principle to explain why a plane wave remains plane while traveling through a uniform medium.

Show how the speed form of Snell's law becomes the index form.

Light travels in glass of refractive index \(1.50\). How far do Huygens wavelets expand in \(2.0\,\mathrm{ns}\)?

Use the speed form of Snell's law to find the refracted angle when light enters glass \((n=1.50)\) from air at \(30^\circ\).

Use Huygens principle to explain why a wave spreads after passing through a narrow opening.

Use the Huygens construction to explain why a ray does not bend at normal incidence when entering a new medium.

A wave enters a faster medium where its speed becomes \(1.25\) times larger. If the incident angle is \(30^\circ\), find the refracted angle using the speed form of Snell's law.

Use a Huygens construction to derive the law of reflection.

Use the Huygens wavefront construction to derive Snell's law in speed form.

A wavefront crosses into a region where the lower part of the wavefront travels more slowly than the upper part. Use Huygens principle to describe what happens to the wavefront and ray direction.

Explain how Huygens principle connects wavefronts with ray optics, and why it also predicts diffraction.

Use Huygens principle to explain why a wavefront bends toward the normal when entering a medium where its speed is halved.