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**6**

The ratio of the indices of refraction of the two media can be expressed as various ratios.

The index of refraction is inversely proportional to the wave speed.

As the wave speed decreases, the index of refraction increases.

The higher the index of refraction, the more it slows downs the light wave speed.

Section 35.5

Slide 36

The previous relationship can be simplified to compare wavelengths and indices: λ1n1 = λ2n2

In air, n1 = 1 and the index of refraction of the material can be defined in terms of the wavelengths.

Section 35.5

Slide 37

n1 sin θ1 = n2 sin θ2

θ1 is the angle of incidence

θ2 is the angle of refraction

The experimental discovery of this relationship is usually credited to Willebrord Snell and is therefore known as Snell’s law of refraction.

Refraction is a commonplace occurrence, so identify an analysis model as a wave under refraction.

Section 35.5

Slide 38

A ray of single-wavelength light incident on the prism will emerge at angle d from its original direction of travel.

d is called the angle of deviation.

F is the apex angle.

Section 35.5

Slide 39

Huygens assumed that light is a form of wave motion rather than a stream of particles.

Huygens’s Principle is a geometric construction for determining the position of a new wave at some point based on the knowledge of the wave front that preceded it.

All points on a given wave front are taken as point sources for the production of spherical secondary waves, called wavelets, which propagate outward through a medium with speeds characteristic of waves in that medium.

After some time has passed, the new position of the wave front is the surface tangent to the wavelets.

Section 35.6

Slide 40

At t = 0, the wave front is indicated by the plane AA.’

The points are representative sources for the wavelets.

After the wavelets have moved a distance cΔt, a new plane BB’ can be drawn tangent to the wavefronts.

Section 35.6

Slide 41

The inner arc represents part of the spherical wave.

The points are representative points where wavelets are propagated.

The new wavefront is tangent at each point to the wavelet.

- Introduction to Light
- Light and Optics
- The Nature of Light
- Nature of Light – Alternative View
- Christian Huygens
- Confirmation of Wave Nature
- Particle Nature
- Dual Nature of Light
- Measurements of the Speed of Light
- Measurement of the Speed of Light – Roemer’s Method
- Roemer’s Method, cont.
- Measurements of the Speed of Light – Fizeau’s Method
- Fizeau’s Method, cont.
- The Ray Approximation in Ray Optics
- Ray Approximation
- Ray Approximation, cont.
- Reflection of Light
- Specular Reflection
- Diffuse Reflection
- Law of Reflection
- Law of Reflection, cont.
- Multiple Reflections
- Retroreflection
- Refraction of Light
- Refraction, cont.
- Refraction of Light, final
- Following the Reflected and Refracted Rays
- Refraction Details, 1
- Refraction Details, 2
- Light in a Medium
- The Index of Refraction
- Index of Refraction, cont.
- Frequency Between Media
- Index of Refraction Extended
- More About Index of Refraction
- Snell’s Law of Refraction
- Prism
- Huygens’s Principle
- Huygens’s Construction for a Plane Wave
- Huygens’s Construction for a Spherical Wave
- Huygens’s Principle and the Law of Reflection
- Huygens’s Principle and the Law of Reflection, cont.
- Huygens’s Principle and the Law of Refraction
- Huygens’s Principle and the Law of Refraction, cont.
- Huygens’s Principle and the Law of Refraction, final
- Dispersion
- Variation of Index of Refraction with Wavelength
- Refraction in a Prism
- The Rainbow
- The Rainbow, cont.
- Observing the Rainbow
- Double Rainbow
- Total Internal Reflection
- Possible Beam Directions
- Critical Angle
- Critical Angle, cont.
- Fiber Optics
- Construction of an Optical Fiber
- Fiber Optics, cont.

- Newton's Laws
- Health Physics
- Resource Acquisition and Transport in Vascular Plants
- Solar Thermal Energy
- Gravitation
- Solar Energy
- Understanding Heat Transfer, Conduction, Convection and Radiation

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