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Light

Light. Students will learn about light. Light. Light is a transverse electromagnetic wave. Consider the electric field portion as transverse up and down and the magnetic field portion as perpendicular side to side.

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Light

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  1. Light Students will learn about light.

  2. Light • Light is a transverse electromagnetic wave. Consider the electric field portion as transverse up and down and the magnetic field portion as perpendicular side to side. • Light has many wave properties: reflection, refraction, diffraction, interference patterns, Doppler effect, color dependent on frequency, and intensity (or brightness) dependent on the amplitude of the waves.

  3. Speed of light • The speed of light in a vacuum (and also in air) is 3 x 10^8 m/s. • Albert Einstein showed that nothing, nowhere, no how can ever every go faster than the speed of light = 3 x 10^8 m/s.

  4. Light as a particle • Sometimes light acts as a particle • Light “particles” are called “photons” • In very dim light, light appears as small pieces or bits • Light energy (as photons): E = hf • H = 6.63 x 10^-34 Joule seconds

  5. Electromagnetic Spectrum Gamma rays 10^19 – 10^21 Hertz 10^-12 m • X rays 10^17 – 10^20 Hertz 10^-10 m • Ultraviolet 10^15 – 10^18 Hertz 10^-7 m • Visible 10^14 – 10^15 Hertz 10^-6 m • Infrared 10^12 – 10^14 Hertz 10^-5 m • Microwave 10^9 – 10^12 Hertz .01 m • FM /TV 10^8 Hertz 3 m • AM 10^6 Hertz 200 m

  6. Dispersion • Dispersion is the spreading of white light into the full spectrum. A prism separates white light into a rainbow of colors. This happens because the index of refraction of the material depends on the wavelength. Different wavelengths are bent to varying degrees. • Violet is bent the most; red is bent the least. • The sky is blue because it is bent the most as sunlight comes through earth’s atmosphere.

  7. Examples of Dispersion • Prism • Rainbow • Diamonds

  8. Polarized light • Ordinary light is unpolarized. It has many vibrations in many planes at once. The electric field vectors vibrate at all angles. • Light can be “filtered” or “polarized” by passing it through parallel slits. Long molecules can be arranged as long slits to achieve this purpose.

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