MODERN OPTICS

Introduction to OpticSCHAPTER 1

PHY 4402Optics is the study of the behavior of light (not necessarily visible light).This behavior can be described by Maxwells equations.

where is the electric field, is the magnetic field, and c is the velocity of light.

PHY 44023Nature of Light

OpticsPHY 4402What is LIGHT?Light is a special type of wavelight or VISIBLE LIGHT is actually a type of something called ELECTROMAGNETIC RADIATION.light has both wave and particle characteristicsLight can be modeled as a wave using wave model of light frequency, wavelength, and velocity (explains most properties of light).Light can be modeled as a particle using particle theory of light photoelectric effect (photons of light produce free electrons).

PHY 4402Visible light is part of the electromagnetic spectrum of waves.The speed of light depends on the medium. Light travels fastest in a vacuum, slower in more denser states of matter, v=c/n.Because light is a periodic wave, it possesses the characteristics of all periodic waves:ReflectionRefraction InterferenceDiffraction

PHY 4402Theories of OpticsLight is an electromagnetic phenomenon described by the same theoretical principles that govern all forms of electromagnetic radiation. Maxwells equations are in the heart of electromagnetic theory & is fully successful in providing treatment of light propagation. Electromagnetic optics provides the most complete treatment of light phenomena in the context of classical optics. Turning to phenomena involving the interaction of light & matter, such as emission & absorption of light, quantum theory provides the successful explanation for light-matter interaction. These phenomena are described by quantum electrodynamics which is the combination of electromagnetic theory with quantum theory. For optical phenomena, this theory also referred to as quantum optics. This theory provides an explanation of virtually all optical phenomena. PHY 4402In the context of classical optics, electromagentic radiation propagates in the form of two mutually coupled vector waves, an electric field-wave & magnetic field wave. It is possible to describe many optical phenomena such as diffraction, by scalar wave theory in which light is described by a single scalar wavefunction. This approximate theory is called scalar wave optics or simply wave optics. When light propagates through & around objects whose dimensions are much greater than the optical wavelength, the wave nature of light is not readily discerned, so that its behavior can be adequately described by rays obeying a set of geometrical rules. This theory is called ray optics. Ray optics is the limit of wave optics when the wavelength is very short.

Quantum OpticsElectromagnetic OpticsWave OpticsRay OpticsPHY 4402Quantum OpticsQuantum optics is a field of research in physics, dealing with the application of quantum mechanics to phenomena involving light and its interactions with matter.deals with light as made up of particles (tiny bundles of energy) called photons and hence inherently is quantized. Quantum optics is the study of the nature and effects of light as quantized photons.Atomic orbitsProbability densitiesEnergy levelsQuantaLasers

PHY 4402Sources of Light

Incandescent light: light produced by heating an object until it glows.

Fluorescence light : light produced by electron bombardment of gas molecules

Bioluminescence: light produced by chemical reactions

Phosphorescence: light produced by light (re-radiating of energy)PHY 4402All the known properties of light can be grouped and classified as:Geometry OpticsWave OpticsQuantum Optics

Properties of LightPHY 4402Geometry Opticsdescribed in terms of straight lines and plane geometry (light travels in straight lines)As long as apertures are much larger than a wavelength of light (and thus wave fronts are much larger than ) the light wave front propagates without distortion (or with a negligible amount)( < dimension of aperture/object)Examples: Rectilinear propagation (light goes in a straight line through a homogeneous medium)Lens and mirrorsFinite SpeedReflection (how light reflects)Refraction (how light acts moving from one medium into another)Dispersion

PHY 4402Reflection Reflection Bouncing back of light waves (change in direction of a wave)The law of reflection says that for specular reflection the angle at which the wave is incident on the surface equals the angle at which it is reflected. Regular reflection mirrors smooth surfaces scatter light very little. Images are clear & exact.Diffuse reflection reflected light is scattered due to an irregular surface.

PHY 4402MirrorsPlane Mirrors Perfectly flatConvex Mirror - Curves outward 2000 Microsoft Clip GalleryLensesConvex Lenses Thicker in the center than edges. Lens that converges (brings together) light rays. Forms real images and virtual images depending on position of the objectConcave Lenses Lens that is thicker at the edges and thinner in the center. Diverges light rays All images are erect and reduced.Vision Eye is a convex lens.Nearsightedness Concave lenses expand focal lengthsFarsightedness Convex lenses shortens the focal length.

Focal PointLensObjectPHY 4402Refraction of LightRefraction Bending of light due to a change in speed. Index of Refraction Amount by which a material refracts light.Prisms Glass that bends light. Different frequencies are bent different amounts & light is broken out into different colors.

PHY 4402Fish-eye view of the World

PHY 4402RainbowsThis rainbow is caused by light being refracted while entering a droplet of water, then reflected inside on the back of the droplet and refracted again when leaving it.In a double rainbow, a second arc is seen outside the primary arc, and has the order of its colors reversed, red facing toward the other one, in both rainbows. This second rainbow is caused by light reflecting twice inside water droplets. The region between a double rainbow is dark, and is known as "Alexander's band" or "Alexander's dark band".Area between rainbows often seen to be darker than elsewhere.Note: rainbow can exist in foreground.

PHY 4402Mirages

Mirages is a real optical phenomenon which can be captured on camera, since light rays actually are refracted to form the false image at the observer's location.

PHY 4402Wave Optics (Physical Optics)deals with the wave nature of light. > dimension of aperture/object (If apertures or obstacles, etc have dimensions comparable to (e.g. < 103 ) then wave front becomes distorted).ExamplesInterferenceDiffractionElectromagnetic characterPolarizationDouble refractionPHY 4402DiffractionDiffraction occurs when a wave encounters an obstacle. It is described as the apparent bending of waves around small obstacles (edge of a barrier) and the spreading out of waves past small openings. New waves are formed from the original, breaks images into bands of light & dark and colors.

The light pattern emerging from a single small rectangular openingPHY 4402Polarization of LightPolarization is the separation of a beam of light so that the vibrations are in one plane.It is an exclusive property of transverse waves.When a light wave is produced, it vibrates in many directions.If a beam of light passes through a polarizing filter, the beam that emerges will vibrate in one plane only and is said to be plane Polarized.When light is reflected from a nonmetallic surface, it is polarized.Which is why polarized sunglasses can be used to eliminate glare

PHY 4402Two set of waves (such as light) can combine with each other to produce a resultant wave. The way in which this combined wave is produced is called interference.A point source produces a spherical wave. If the light from two point sources overlaps, the interference pattern depends on the wavelength and on the separation of the point sources. Constructive vs. destructive interference.

Interference

PHY 4402 2003 Mike Maloney22when light encounter a surface/ boundary, they are partially transmitted and partially reflected.Therefore, an object does not need to emit photons itself to be seen, it just has to reflect light back to our eyes where we can detect it.

PHY 4402Color of LightObjects that do not allow light to pass through them are called opaque.Light is either reflected or absorbed. Color of opaque objects is color it reflects.Objects that allow light to pass through them are considered transparent.Light transmitted because of no scatteringColor transmitted is color you see. All other colors are absorbed.Objects in between are called translucent.Light is scattered and transmitted some.PHY 4402Color of LightColor of ObjectsWhite light is the presence of ALL the colors of the visible spectrum.Black objects absorb ALL the colors and no light is reflected back.Primary Colors of LightThree colors that can be mixed to produce any other colored lightRed + blue + green = white lightComplimentary Colors of LightTwo complimentary colors combine to make white light-Magenta,Cyan,Yellow

2000 Microsoft Clip Gallery

PHY 4402 2003 Mike Maloney25ColorDifferent objects may emit different wavelengths of EM radiation, so we would see that light as different colors.The light we could see is known as visible or white light.The light is not really white, the white we see is a combination of all the colors of the rainbow (R-O-Y-G-B-I-V).When all of these light waves are combined we see white light.PHY 4402 2003 Mike Maloney26Color Reflection & TransmissionSo if we see something as WHITE, that means It reflected back all the wavelengths of light to our eyesIf we see something as RED or BLUEIt reflected only the RED or only the BLUE wavelengthsThe others were absorbed.And if we see something as black?It did not reflect back any of the light.Filters work in a similar way.Red filters only let RED light thru.Blue let only BLUE light thru.

PHY 4402At the end of Chapter 1Can youDescribe what is optics?What is the source of light?Differentiate geometrical optics, wave optics and quantum optics?Give example of geometrical optics, wave optics and quantum opticsPHY 4402