Light - PowerPoint PPT Presentation

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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

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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.

• 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

• 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

• 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

Gamma rays10^19 – 10^21 Hertz10^-12 m

• X rays 10^17 – 10^20 Hertz10^-10 m

• Ultraviolet10^15 – 10^18 Hertz10^-7 m

• Visible10^14 – 10^15 Hertz10^-6 m

• Infrared10^12 – 10^14 Hertz10^-5 m

• Microwave10^9 – 10^12 Hertz.01 m

• FM/TV10^8 Hertz3 m

• AM10^6 Hertz200 m

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.

• Prism

• Rainbow

• Diamonds

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.