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**3**

d is the distance between the wheel and the mirror.

Δt is the time for one round trip.

Then c = 2d / Δt

Fizeau found a value of

c = 3.1 x 108 m/s.

Section 35.2

Slide 14

Ray optics (sometimes called geometric optics) involves the study of the propagation of light.

It uses the assumption that light travels in a straight-line path in a uniform medium and changes its direction when it meets the surface of a different medium or if the optical properties of the medium are nonuniform.

The ray approximation is used to represent beams of light.

Section 35.3

Slide 15

The rays are straight lines perpendicular to the wave fronts.

With the ray approximation, we assume that a wave moving through a medium travels in a straight line in the direction of its rays.

Section 35.3

Slide 16

If a wave meets a barrier, with λ<<d, the wave emerging from the opening continues to move in a straight line.

d is the diameter of the opening.

There may be some small edge effects.

This approximation is good for the study of mirrors, lenses, prisms, etc.

Other effects occur for openings of other sizes.

See fig. 35.4 b and c

Section 35.3

Slide 17

A ray of light, the incident ray, travels in a medium.

When it encounters a boundary with a second medium, part of the incident ray is reflected back into the first medium.

This means it is directed backward into the first medium.

For light waves traveling in three-dimensional space, the reflected light can be in directions different from the direction of the incident rays.

Section 35.4

Slide 18

Specular reflection is reflection from a smooth surface.

The reflected rays are parallel to each other.

All reflection in this text is assumed to be specular.

Section 35.4

Slide 19

Diffuse reflection is reflection from a rough surface.

The reflected rays travel in a variety of directions.

A surface behaves as a smooth surface as long as the surface variations are much smaller than the wavelength of the light.

Section 35.4

Slide 20

The normal is a line perpendicular to the surface.

- 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.

- Heat-Energy on the Move
- Sound
- Geophysical Concepts, Applications and Limitations
- Mechanics Lecture
- Upcoming Classes
- Waves & Sound
- Thermal Energy

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