Geometrical Optics

• Optics is the branch of physics concerning the behavior and properties of light.
• This includes light's interaction with matter.
• Optics also covers building instruments that use or detect light.
• Optical phenomena explained by optics include rainbows, halos, and mirages.
• Common technologies/applications include lenses, microscopes, telescopes, lasers, and fiber optics.
• Optics typically describes the properties of visible, ultraviolet, and infrared light.
• Light has both wave-like and particle-like properties.
• Optics is categorized as a branch of electromagnetism and quantum mechanics.

Geometrical Optics

• Also known as ray optics.
• Describes light as traveling in straight lines called rays.
• Describes reflection, refraction, total internal reflection, lenses, image formation, and optical instruments.
• Reflection involves a change in a wavefront's direction at the interface between two media.
• The wavefront returns into the medium from which it originated.
• Specular reflection occurs on smooth surfaces like mirrors.
• Diffuse reflection occurs on rough surfaces.
• Refraction is the bending of light as it passes from one transparent substance into another.
• Snell's Law relates the angles of incidence and refraction to the refractive indices of the two media.
• Lenses use refraction to focus light and form images.
• Converging lenses focus parallel light rays to a point.
• Diverging lenses spread parallel light rays.
• Focal length is the distance from the lens where parallel rays converge or appear to diverge.
• Optical instruments use lenses and mirrors to form images (e.g., cameras, telescopes, microscopes).

Wave Optics

• Addresses phenomena not explained by geometric optics, like diffraction, interference, and polarization.
• Describes diffraction, interference, thin films, interferometry, and holography.
• Diffraction is the bending of waves around obstacles or through narrow openings.
• Interference happens when two or more waves overlap in space.
• Constructive interference: waves are in phase, resulting in a larger amplitude.
• Destructive interference: waves are out of phase, resulting in a smaller amplitude.
• Thin films can produce interference effects from reflections on the film's surfaces.
• Interferometry makes precise measurements of distances, wavelengths, and refractive indices using light interference.
• Holography records and reconstructs wavefronts to create 3D images.

Quantum Optics

• Studies the quantum mechanical properties of light and its interaction with matter.
• Describes photons, lasers, quantum entanglement, and quantum computing.
• Light is composed of photons, which have energy and momentum.
• Lasers produce coherent light with a well-defined wavelength and phase.
• Quantum entanglement links two or more particles, sharing the same fate regardless of distance.
• Quantum computing uses quantum mechanical phenomena for computations.

Electromagnetic Spectrum

• The range of all possible frequencies of electromagnetic radiation.
• Includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
• Radio waves have the longest wavelengths and lowest frequencies.
• Microwaves are used in microwave ovens, radar, and communication.
• Infrared radiation is associated with heat.
• Visible light is the portion of the electromagnetic spectrum that is visible to the human eye.
• Ultraviolet radiation can cause sunburns and skin cancer.
• X-rays are used in medical imaging.
• Gamma rays have the shortest wavelengths and highest frequencies.

Polarization

• Property of transverse waves describing the direction of oscillations.
• Unpolarized light has oscillations in all directions perpendicular to propagation.
• Polarized light has oscillations in a single direction.
• Polarization can be achieved through reflection, refraction, dichroism, and scattering.
• Polarizing filters block light with a particular polarization.
• Liquid crystal displays (LCDs) use polarized light to control pixel brightness.

Optical Instruments

• Use lenses and mirrors to form images of objects.
• Cameras use lenses to focus light onto a sensor or film.
• Telescopes use lenses or mirrors to collect and focus light from distant objects.
• Microscopes use lenses to magnify small objects.
• Spectrometers use diffraction gratings or prisms to separate light into its component wavelengths.

Applications of Optics

• Optics is applied in science, engineering, and medicine.
• Fiber optics transmit data over long distances.
• Lasers are used in manufacturing, medicine, and telecommunications.
• Optical sensors measure temperature, pressure, and other physical quantities.
• Imaging techniques like MRI and CT scans use optical principles to create internal body images.
• Displays and lighting rely on optical principles to generate and control light.