# Light Students will learn about light Light Light

• Slides: 8

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

Examples of Dispersion • 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.