Electromagnetic Waves and Light

Electromagnetic Waves Electromagnetic waves do not require a medium to travel. They are created by oscillating (moving) electrons generating changing electrical and magnetic fields.

Electromagnetic Waves Travel at the speed of light: 300,000 km/s in a vacuum. Light can behave like a particle – called a photon.

Electromagnetic Waves Electromagnetic Spectrum is the range of frequencies of electromagnetic waves.

Electromagnetic Spectrum Radio Waves – lowest frequency /energy; longest wavelength Microwaves Infrared waves

Electromagnetic Waves Visible light: Red – lowest energy/frequency, longest wavelength Orange Yellow Green Blue Indigo Violet – highest energy/frequency, shortest wavelength

Electromagnetic Waves Ultraviolet – can cause skin damage/cancer; helps body make vitamin D; used to kill bacteria X-Rays – used in medical imaging Gamma Rays – used in radiation therapies for cancer

Light Objects can absorb light, reflect light, or let light pass through them. Opaque – no light goes through, all is absorbed Translucent – some light passes through Transparent – almost all light passes through

Light Prisms work by refracting light and separating white light into the “rainbow” of colors (frequencies). Mirages occur when you have light passing through air of different densities (temperature).

Light When humans see color, they see the only that frequency of light being reflected back to their eyes, the rest of the color frequencies are absorbed.

Light White light is the combination of all colors. Humans see white when all light frequencies are reflected back. Black is all the frequencies of light being absorbed and none reflected.

Light Primary colors of light are red, green, and blue. Mixing these three colors of light produces white light.

Light Pigments are colored material that absorbs some colors and reflects others. Primary pigments are magenta, cyan, and yellow. Mixing all the primary pigments produces black.

Light Lasers are formed from coherent light – light of only one wavelength that travels with its crests and troughs aligned. Polarized light is also traveling in one direction. Polarized filters (used in some sunglasses) reduce glare by eliminating all but one direction of light.

Light Optical fibers rely on total internal reflection – when light travels from one medium to another is actually completely reflected at the boundary between the mediums. Used in communication wires, medical equipment, etc. Can transmit large amounts of data in a small fiber.