Understanding Light and the Electromagnetic Spectrum

• Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum.
• Light's properties include intensity, propagation direction, frequency or wavelength, and polarization.
• Light exhibits wave-particle duality, behaving as both a wave and a stream of particles called photons.

Properties of Light

• Light travels in straight lines.
• Light can be reflected, refracted, diffracted, and polarized.
• The speed of light in a vacuum is a fundamental physical constant, approximately 299,792,458 meters per second.

Electromagnetic Spectrum

• The electromagnetic spectrum encompasses all types of electromagnetic radiation.
• It is organized by frequency (ν) and wavelength (λ), which are inversely proportional (c = λν, where c is the speed of light).
• The spectrum includes, from lowest to highest frequency: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
• Visible light is the portion of the spectrum that the human eye can detect, ranging from approximately 400 nm (violet) to 700 nm (red).

Reflection and Refraction

• Reflection occurs when light bounces off a surface.
• The law of reflection states that the angle of incidence equals the angle of reflection.
• Refraction is the bending of light as it passes from one medium to another due to a change in speed.
• Snell's law describes the relationship between the angles of incidence and refraction and the refractive indices of the two media (n1sinθ1 = n2sinθ2).
• The refractive index of a medium is the ratio of the speed of light in a vacuum to its speed in the medium (n = c/v).

Optics

• Optics is the branch of physics that studies the behavior and properties of light.
• It includes the study of how light interacts with matter and the design of instruments that use light.
• Geometric optics deals with light as rays and is used to analyze lenses, mirrors, prisms, and other optical components.
• Physical optics (wave optics) deals with the wave nature of light and explains phenomena like interference, diffraction, and polarization.
• Lenses focus or diverge light through refraction, forming images.
• Mirrors reflect light to form images; plane mirrors produce virtual images, while curved mirrors (concave and convex) can produce real or virtual images.

Sources of Light

• Natural sources of light include the sun, stars, lightning, and bioluminescent organisms.
• Artificial sources of light include incandescent bulbs, fluorescent lamps, LEDs, and lasers.
• Incandescent light is produced by heating a filament until it glows.
• Fluorescent light is produced by exciting a gas with electricity, causing it to emit ultraviolet light, which then strikes a phosphor coating that emits visible light.
• LEDs (light-emitting diodes) produce light through electroluminescence in a semiconductor material.
• Lasers produce coherent, monochromatic, and collimated light through stimulated emission.