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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

Light

Students will learn about light.


Light1
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.


Speed of light
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.


Light as a particle
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


Electromagnetic spectrum
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


Dispersion
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.


Examples of dispersion
Examples of Dispersion

  • Prism

  • Rainbow

  • Diamonds


Polarized light
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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