Introduction to Optics

• Optics is the branch of physics that studies the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it
• Optics usually describes the behaviour of visible, ultraviolet, and infrared light
• Because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties
• Optics can be divided into different categories, studying different aspects of light.

Physical optics

• Physical optics treats light as a wave
• It studies phenomena such as interference, diffraction, polarization, and scattering

Geometric optics

• Geometric optics treats light as a collection of rays that travel in straight lines and bend when they pass through or reflect from surfaces
• It describes phenomena such as reflection, refraction, lenses, prisms, and optical instruments such as telescopes and microscopes

Quantum optics

• Quantum optics deals with the particle nature of light (photons)
• It studies phenomena such as the photoelectric effect, blackbody radiation, and the interaction of light with matter at the atomic level

Electromagnetic optics

• Electromagnetic optics is an area of optics that studies the electromagnetic nature of light
• It incorporates the principles of electromagnetism, light is described as an electromagnetic wave
• It examines phenomena like polarization, interference, and diffraction from an electromagnetic perspective

Linear optics

• Studies the behaviour of light in linear media, where the optical properties of the material do not change with the intensity of light
• Deals with phenomena such as refraction, reflection, and image formation with lenses and mirrors

Nonlinear optics

• Studies the behaviour of light in nonlinear media, where the optical properties of the material change with the intensity of light
• Deals with phenomena such as second harmonic generation, sum and difference frequency generation and self-focusing

Reflection

• Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated
• Specular reflection is reflection from a smooth surface
• Diffuse reflection is reflection from a rough surface

Refraction

• Refraction is the change in direction of a wavefront as it passes from one medium to another
• Snell's law describes the relationship between the angles of incidence and refraction, and the refractive indices of the two media

Lenses

• A lens is an optical device that focuses or diverges light
• Convex lenses converge light rays
• Concave lenses diverge light rays
• Lenses are used in a wide variety of optical instruments, such as cameras, telescopes, and microscopes

Prisms

• A prism is an optical device that disperses light, separating it into its component colors
• Prisms are used in spectroscopes and other optical instruments

Optical instruments

• Optical instruments use lenses, mirrors, and prisms to manipulate light and form images
• Examples of optical instruments include cameras, telescopes, microscopes, and binoculars

Interference

• Interference is the phenomenon that occurs when two or more waves overlap in space
• Constructive interference occurs where the waves are in phase, resulting in an increase in amplitude
• Destructive interference occurs where the waves are out of phase, resulting in a decrease in amplitude

Diffraction

• Diffraction is the phenomenon that occurs when a wave encounters an obstacle or aperture
• The wave bends around the obstacle or spreads out after passing through the aperture
• Diffraction is responsible for the blurring of images

Polarization

• Polarization is the phenomenon that occurs when the electric field vector of a light wave is restricted to a single plane
• Polarized light can be produced by passing light through a polarizer
• Polarizers are used in sunglasses, cameras, and other optical instruments

Scattering

• Scattering is the phenomenon that occurs when light interacts with matter and is redirected in different directions
• Rayleigh scattering is the scattering of light by particles that are much smaller than the wavelength of the light
• Mie scattering is the scattering of light by particles that are comparable in size to the wavelength of the light

Applications of optics

• Optical instruments (cameras, telescopes, microscopes)
• Fiber optics (telecommunications, medical imaging)
• Lasers (medicine, manufacturing, telecommunications)
• Holography (3D imaging)
• Spectroscopy (chemical analysis)
• Optical data storage (CDs, DVDs, Blu-ray discs)
• Photovoltaics (solar energy)
• Displays (LCDs, LEDs)
• Lighting