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Fundamental Properties of Light

Fundamental Properties of Light. Introduction to Physical Optics. What is Light?. To understand physical optics, let’s review how we think about and measure light, which is part of electromagnetic radiation. Ultraviolet Rays. Infrared (IR). Radio wave. Gamma Rays. Microwave. X Rays.

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Fundamental Properties of Light

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  1. Fundamental Properties of Light Introduction to Physical Optics Chester F. Carlson Center for Imaging Science

  2. What is Light? • To understand physical optics, let’s review how we think about and measure light, which is part of electromagnetic radiation. Chester F. Carlson Center for Imaging Science

  3. Ultraviolet Rays Infrared (IR) Radio wave Gamma Rays Microwave X Rays Light Electromagnetic Radiation • EM radiation is made up of an electric field and a magnetic field. • Particle-wave duality of EM radiation. • Light as a particle • Light as a wave (physical optics) • Includes x-rays as well as light, IR (heat) and radio waves. 10-15 m 10-2 m 103 m 10-6 m Chester F. Carlson Center for Imaging Science

  4. E B Direction of Travel • Light is an electromagnetic wave because it requires two interdependent fields to propagate. • Both electrical (E) and magnetic (B) waves must exist for light to propagate. E and B are perpendicular to each other and to the direction of motion. • The electric field has the greater effect on materials, and so we ignore the effect of the magnetic field from this point on. Chester F. Carlson Center for Imaging Science

  5. Optics • Optics contains two areas of study: • Geometrical Optics • Physical Optics • Geometrical optics, or ray optics, is the study of light that travels as a “ray,” in straight lines. • Light rays passing through lenses and bouncing off mirrors Chester F. Carlson Center for Imaging Science

  6. What is Physical Optics? • Physical optics, or wave optics, is the study of how light interacts with objects similar in size to its wavelength. • Light energy travels as a wave (not a ray). • Wave optics concerns the characteristics of light such as wavelength, intensity, phase, and orientation. Chester F. Carlson Center for Imaging Science

  7. Wavelength  • Wavelength is the distance between two identical points on a wave. (,lambda) Chester F. Carlson Center for Imaging Science

  8. Frequency time • Frequency is the number of cycles per unit of time. (, nu) • It is inversely proportional to the wavelength. unit of time Chester F. Carlson Center for Imaging Science

  9. Wavelength andFrequency Relation  = v/ • Wavelength is proportional to the velocity, v. • Wavelength is inversely proportional to the frequency. • eg. AM radio wave has a long wavelength (~200 m), therefore it has a low frequency (~KHz range). • In the case of EM radiation in a vacuum, the equation becomes c Where c is the speed of light (3 x 108m/s) Chester F. Carlson Center for Imaging Science

  10. Photons • Photons are little “packets” of energy. • Each photon’s energy is proportional to its frequency. • A photon’s energy is represented by “h” E = h Energy = (Planck’s constant) x (frequency of photon) Chester F. Carlson Center for Imaging Science

  11. Transverse Wave Travels perpendicular to change of amplitude. E B Direction of Travel Light Wave • The case of light: • Light waves are called electromagnetic waves because they contain two types of energy that change amplitudes. • Both electrical and magnetic energy vary perpendicular to each other. • Light is a transverse wave because the direction of travel is perpendicular to the amplitude change of BOTH electrical and magnetic fields. Chester F. Carlson Center for Imaging Science

  12. Higher Intensity Lower Intensity Light Intensity • Intensity of a monochromatic light relates to the brightness of that light. • The intensity of an electromagnetic wave is proportional to the amplitude squared. Chester F. Carlson Center for Imaging Science

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