Trivia Question According to Wikipedia, in what year was endoscopy first developed? Endoscopy (looking inside) means looking inside the body for medical reasons. 1806 1911 (c) 1950 (d) 1957 (e) 1975

Trivia Question According to Wikipedia, in what year was endoscopy first developed? Endoscopy (looking inside) means looking inside the body for medical reasons. (a) 1806 by Philipp Bozzini in Mainz with his introduction of a "Lichtleiter" (light conductor) "for the examinations of the canals and cavities of the human body“. Note this PRE-DATES the invention of the light bulb. (b) (c) (d) (e)

The grand overview of Optics/Photonics Historical Development: Ray Optics → Wave Optics → EM Optics → Quantum Optics. Ray Optics is an approximation of Wave Optics in which wavelength short compared to other dimensions (focal lengths, diameter of optical components, etc.) so that Diffraction can be ignored. Wave Optics – Is needed to describe phenomena such as INTERFERENCE, DIFFRACTION, Phase and Group velocities, and one of the focuses of this week’s material DISPERSION meaning that the refractive index in materials VARIES with the wavelength (or equivalently ‘color’ of light).

Explanation of WHY prism breaks light into colors REQUIRES the introduction of the concept of waves. This is the concept of DISPERSION…. Namely that the refractive index of a material depends on the COLOR of the light.

Postulates of Wave Optics Light travels as waves with a speed of light in a vacuum given by co. Speed of light in a medium determined by refractive index n Optical wave is expressed mathematically as a wavefunction y(r,t) which satisfies the wave equation: Of course, we know that the wavefunction is physically the electric and magnetic fields of an electromagnetic wave.

Postulates of Wave Optics Principle of superposition: ( we will return to this later) Optical Intensity (optical power/ unit area) [W/cm2] is proportional to average of square of waveform. Average over times much longer then duration of optical cycle 1/ν. Optical power (Watts) calculated as power flowing through area perpendicular to direction of propagating wave. Optical energy: Integrate optical power over some period of time. (Energy/ time=Watts)

Plane Waves Wave extends laterally To infinity Propagation Direction Wave Equation

Definitions of k, ω, λ, ν Click on the animation of the wave below…. E and B field wave Imagine taking a “snapshot” in time of the propagating wave λ Wavelength is the distance between the ‘peaks’ in the wave. For Frequency, imagine standing at a fixed point in space and counting the time delay between ‘peaks’ of the wave passing by you.

Relations for Plane Waves k

Wavefronts correspond to locations of the wave of CONSTANT PHASE Rays from ray optics are PERPENDICULAR to wavefronts. This is even true is wavefronts are curved.

Complex Numbers

Polarizability Use ELECTRIC FIELD of light rather than + charge E External electric Field moves positive charges to one side and negative to another. What if we have MANY of these polarizable molecules in a material

Polarizability E Induced E The INDUCED electric field tends to partial CANCEL the applied external Electric field Many times, one defines the “Polarizability” vector as

Polarization charge Note: there tends to be a local cancelation of the polarized charge unless there is a DIVERGENCE of the polarizability. For Plane waves in a homogeneous, isotropic material, there should be no divergence of polarization.

Imaginary Refractive Index Frequency CONSTANT as light moves from one medium to another Wavelength CHANGES from one medium to another

Change of wavelength with nr Speed fast, smaller refractive index Speed slow, larger refractive index

Capacitors come in all shapes and sizes…. Similar principle can be used for “touch screens” of tablets, smart phones, etc.

Capacitors STORE charge or EQUIVALENTLY Electric field. Parallel plate capacitor Note: it is ASSUMED that charge is equal and opposite on the two plates If an electromagnetic wave passes through a medium with electric charges, the E field from the wave will exert a force on the charges to make them move (ie. current) which could be used to perform WORK. Energy is STORED in the electric field of an electromagnetic wave

Inductors come is various shapes and sizes

Inductors store energy in form of magnetic field B Energy is stored in the MAGNETIC field of an electromagnetic wave. In a vacuum, there is no flow of ‘real’ current’, but instead displacement current.