Interference pattern produced with a Michelson interferometer. Bright bands are the result of constructive interference while the dark bands are the result of destructive interference.

Interference pattern produced with a Michelson interferometer.

Wave optics is the branch of optics concerned with interference, diffraction, polarization, and other phenomena for which the ray approximation of geometric optics is not valid. As with geometric optics, there are many medical and life science research applications of wave optics ranging from the use of X-ray crystallography to study proteins and nucleic acids to many applications of interferometry in medical and biological imaging. On the new MCAT if you encounter a passage on something like optical coherence tomography (OCT), a radiology technique for visualizing internal tissue microstructures, or differential interference contrast (DIC) microscopy, remember that such a passage is not going to be testing whether you have specific prior knowledge of the technologies but whether you can apply the fundamental principles of wave optics to comprehend what you are reading.

WikiPremed Resources

Wave Optics Cards
Chapter from the Wisebridge Learning System for Physics

Light & Optics Practice Items
Problem set for Light & Optics in PDF format

Answer Key
Answers and explanations

Wave Optics Images
Image gallery for study with links to larger teaching JPEGs for classroom presentation

Question Drill for Wave Optics
Conceptual Vocabulary Self-Test

Basic Terms Crossword Puzzle

Basic Puzzle Solution

Learning Goals


Understand diffraction in terms of Huygens' Principal.

Comprehend how interference produces the pattern of light and dark fringes in Young's double slit diffraction experiment.

Remember the distinction between hard and soft reflection.

Be able to describe how thin film interference produces the iridescent colors of soap bubbles. Be able to extend this understanding to similar interference phenomona such as observed with an air wedge.

Understand how the Michelson interferometer can be used to measure very small distances.

With regard to the Fraunhofer type of pattern produced with single slit diffraction, understand what determines the width of the central fringe and the location of maxima and minima.

Be able to apply principles from single slit diffraction to understanding the pattern of an airy disc which governs the resolution of optical instruments such as microscopes and astronomical telescopes. Remember Rayleigh's criterion.

Be able to recall the means by which polarized light may be produced. Be familiar with Brewster's angle.

Suggested Assignments

Review the basic terms for wave optics using the question server. Complete the fundamental terms crossword puzzle. Here is the solution to the puzzle.

Study the physics cards for wave optics.

Take a review tour of wave optics web resources.

Conceptual Vocabulary for Wave Optics

Wave optics
Physical or wave optics, is the branch of optics which studies interference, diffraction, polarization, and other phenomena for which the ray approximation of geometric optics is not valid.
Interference is the superposition of two or more waves that results in a new wave pattern.
Monochromatic refers to electromagnetic radiation of a single wavelength.
Coherence is the property of wave-like states that enables them to exhibit interference. It is a measure of how perfectly the waves can cancel due to destructive interference.
Diffraction grating
A diffraction grating is an optical component with a surface covered by a regular pattern of parallel lines, typically with a distance between the lines comparable to the wavelength of light.
Polarization is the property of electromagnetic waves that describes the direction of the transverse electric field.
Double-slit experiment
In the double-slit experiment, light is shone at a solid thin plate that has two slits cut into it. A photographic plate is set up to record what comes through those slits.
A polarizer is a device that converts an unpolarized or mixed-polarization beam of electromagnetic waves into a beam with a single polarization state.
Interferometry is the technique of superposing two or more waves, to detect differences between them.
Huygens-Fresnel principle
The Huygens-Fresnel principle recognizes that each point of an advancing wave front is in fact the center of a fresh disturbance and the source of a new train of waves.
Michelson interferometer
The Michelson interferometer is a common configuration for optical interferometry in which an interference pattern is produced by splitting a beam of light into two paths, bouncing the beams back and recombining them.
Brewster's angle
At the angle of incidence known as Brewster's angle, light for which the electric field of the light waves lies in the same plane as the incident ray and the surface normal cannot be reflected with polarization.
Newton's rings
The phenomenon of Newton's rings is an interference pattern caused by the reflection of light between two surfaces - a spherical surface and an adjacent flat surface.
A wavefront is the locus of points in a wave having the same phase.
Airy disc
The Airy disc is the diffraction pattern resulting from a uniformly illuminated circular aperture.
Birefringence is the decomposition of a ray of light into an ordinary ray and an extraordinary ray when it passes through certain types of material, such as calcite crystals or boron nitride, depending on the polarization of the light.
Superposition principle
The principle of superposition states that, for a linear system, a linear combination of solutions to the system is also a solution to the same linear system.
Linear polarization
Linear or plane polarization of electromagnetic radiation is a confinement of the electric field vector or magnetic field vector to a given plane along the direction of propagation.
Beam splitter
A beam splitter is an optical device that splits a beam of light in two. It is the crucial part of most interferometers.
Polarimetry is the measurement of the polarisation of light.
Fraunhofer diffraction
Fraunhofer diffraction is a form of wave diffraction, which occurs when field waves are passed through an aperture or slit, causing only the size of an observed aperture image to change.
Fresnel diffraction
Fresnel diffraction is a process of diffraction which occurs when a wave passes through an aperture and diffracts in the near field, causing any diffraction pattern observed to differ in size and shape, relative to the distance.
Plane wave
A plane wave is a constant-frequency wave whose wavefronts are infinite parallel surfaces of constant amplitude normal to the phase velocity vector.
Circular polarization
Circular polarization of electromagnetic radiation is a polarization such that the tip of the electric field vector, at a fixed point in space, describes a circle as time progresses.
Elliptical polarization
Elliptical polarization is the polarization of electromagnetic radiation such that the tip of the electric field vector describes an ellipse in any fixed plane intersecting, and normal to, the direction of propagation.
Advanced terms that may appear in context in MCAT passages
Interferometric visibility
The interferometric visibility quantifies the contrast of interference in any system which has wave-like properties.
Diffraction limited
Diffraction limited describes an optical system with the ability to produce images with angular resolution as good as the instrument's theoretical limit.
Creeping wave
A creeping wave is the wave that is diffracted around the shadowed surface of a smooth body such as a sphere.
Point spread function
The point spread function describes the response of an imaging system to a point source or point object. The PSF in many contexts can be thought of as the extended blob in an image that represents an unresolved object.
Wave plate
A wave plate is an optical device that alters the polarization state of a light wave travelling through it.
Faraday effect
The Faraday effect is a magneto-optical phenomenon in which the rotation of the plane of polarization is proportional to the intensity of the component of the magnetic field in the direction of the beam of light.
Fourier optics
The approach of Fourier optics stems from the fact that in source-free regions, electromagnetic fields may be expressed in terms of a spectrum of propagating and evanescent plane waves.
Mach-Zehnder interferometer
The Mach-Zehnder interferometer is a device used to determine the phase shift caused by a small sample which is placed in the path of one of two collimated beams from a coherent light source.
Schaefer-Bergmann diffraction
Schaefer-Bergmann diffraction is the resulting diffraction pattern of light interacting with sound waves in transparent crystals or glasses.
Échelle grating
An Échelle grating is a type of diffraction grating which is characterised by a relatively low grooves density but is optimised for high diffraction orders.
Pockels effect
The Pockels effect produces birefringence in an optical medium induced by a constant or varying electric field.