PHYS 012A Lecture Notes - Lecture 26: Geometrical Optics, Total Internal Reflection, Retroreflector
12 Jun 2018
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Chapter 35: Geometric Optics
Intro to Light
- Light is a form of electromagnetic radiation and is basic to almost all life on Earth.
The Nature of Light
- Particles were either emitted by the object being viewed or emanated from the eyes of the
viewer.
Nature of Light – Alternative View
- Huygens argued that light may be some sort of a wave motion.
o Thought light was a type of vibratory motion
- Young showed that light rays interfere with each other and that this cannot be explained by
particles.
Confirmation of Wave Nature
- Maxwell asserted that light was a form of high-frequency electromagnetic wave and Hertz
confirmed this.
Particle Nature
- The photoelectric effect was a major phenomenon not explained by waves.
o When light strikes a metal surface, electrons are sometimes ejected from the surface.
o The kinetic energy of the ejected electron is independent of the intensity of the light.
- By Einstein: e = hf
Dual Nature of Light
- Light exhibits the characteristics of a wave in some situations and the characteristics of a particle
in other situations.
Measurements of the Speed of Light
- C = 3.00 x 106
- Huygens estimated c to be 2.3 x 106
- Fizeau estimated c to be 3.1 x 106
The Ray Approximation in Ray Optics
- Ray optics (geometric optics) involves the study of the propagation of light
- The ray approximation is used to represent beams of light
Ray Approximation
- The rays are straight lines perpendicular to the wave fronts.
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- D is the diameter of the opening. For smaller openings,
where λ is comparable to d, the ray approximation
fails, and we must consider the full wave nature of
light. This leads to phenomena like diffraction and
interference, which we will consider soon.
Reflection of Light
- A ray of light, the incident ray, travels in a medium.
- When it encounters a boundary with another
medium, part of the incident ray is reflected to the
first medium.
Law of Reflection
Specular Reflection is reflection from a smooth surface and the reflected rays are parallel to each other.
Diffuse Reflection is reflection from a rough surface and the reflected rays travel in a variety of
directions.
Multiple Reflections
- The incident ray strikes the first mirror. The reflected ray is directed toward the second mirror.
There is a second reflection from the second mirror.
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Light is a form of electromagnetic radiation and is basic to almost all life on earth. Particles were either emitted by the object being viewed or emanated from the eyes of the viewer. Huygens argued that light may be some sort of a wave motion: thought light was a type of vibratory motion. Young showed that light rays interfere with each other and that this cannot be explained by particles. Maxwell asserted that light was a form of high-frequency electromagnetic wave and hertz confirmed this. Light exhibits the characteristics of a wave in some situations and the characteristics of a particle in other situations. Huygens estimated c to be 2. 3 x 106. Fizeau estimated c to be 3. 1 x 106. Ray optics (geometric optics) involves the study of the propagation of light. The ray approximation is used to represent beams of light. The rays are straight lines perpendicular to the wave fronts. D is the diameter of the opening.
