Electromagnetic Spectrum Image.

Electromagnetic waves consist of synchronized oscillations of electric and magnetic fields that propagate at the speed of light through a vacuum. Produced whenever charged particles are accelerated, electromagnetic waves can subsequently interact with charged particles. In the quantum theory of electromagnetism, light consists of photons. The energy of an individual photon is quantized and is greater for photons of higher frequency.

A thorough descriptive understanding of the electromagnetic spectrum is essential for the MCAT, along with a facility for carrying out calculations involving wavelength, wave speed and frequency involving light. An essential theme for focus is the interaction of electromagnetic waves with matter such as production of photons in the transition of electrons to lower energy levels in an atom. Other important examples include the interaction of ultraviolet and visible light photons with conjugated organic molecules and absorption of infrared radiation in line with transitions between vibrational states in chemical bonds. Additionally, the interaction of electromagnetic radiation with biological systems is an important theme, especially regarding ultraviolet and higher frequencies which can cause direct molecular damage.

WikiPremed Resources

Electromagnetic Waves 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

The Properties of Light Images
Image gallery for study with links to larger teaching JPEGs for classroom presentation

Question Drill for The Properties of Light
Conceptual Vocabulary Self-Test

Basic Terms Crossword Puzzle

Basic Puzzle Solution

Learning Goals


Be able to describe the speed of light in a vacuum as a fundamental constant.

Be able to give a conceptual summary of the meaning of the electric permittivity and magnetic permeability of space.

Understand basic properties of electromagnetic waves such as their transverse wave nature, the ability to travel in a vacuum, and polarizability.

Be able to identify the transitions as you move up in frequency through the electromagnetic spectrum from radio waves to gamma rays.

Possess a good comfort level carrying out basic harmonic wave computations involving wave speed, frequency, and wavelength in the context of electromagnetic radiation.

Understand the significance of particle-wave duality in the context of light and be able to compute the energy of a photon based on its frequency.

Understand basic problem solving involving reflection of light.

Know Snell's Law backwards and forwards and how to solve the basic conceptual and quantitative problems involving the transmission of light between media.

Be able to explain what is happening with the dispersion of light by a prism.

Be able to find the critical angle for light traveling between two media.

Suggested Assignments

Review the basic terms for the properties of light using the question server. Complete the fundamental terms crossword puzzle. Here is the solution to the puzzle.

Study the physics cards for the properties of light.

Perform the practice items for light & optics. These practice items also include some questions from geometric and wave optics. Here is the answer key for the practice items.

In In ExamKrackers Physics, read pp. 129-145. This chapter covers properties of light as well as wave optics. Perform practice items 105-112 on pg. 146.

Take a review tour of the properties of light web resources.

Conceptual Vocabulary for The Properties of Light

Light is electromagnetic radiation.
Reflection is the change in direction of a wave front at an interface between two dissimilar media so that the wave front returns into the medium from which it originated.
Electromagnetic spectrum
The electromagnetic spectrum is the range of all possible electromagnetic radiation.
Visible spectrum
The visible spectrum is the portion of the electromagnetic spectrum that can be detected by the human eye.
Infrared radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. The name means below red.
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than soft X-rays.
X-rays are a form of electromagnetic radiation with a wavelength in the range of 10 to 0.01 nanometers. They are a form of ionizing radiation.
Gamma ray
Gamma rays are forms of electromagnetic radiation or light emissions of a specific frequency produced from sub-atomic particle interaction, such as electron-positron annihilation and radioactive decay.
Refraction is the change in direction of a wave due to a change in its speed.
Angle of incidence
The angle of incidence is a measure of deviation of a ray to a surface from straight on.
Diffuse reflection
Diffuse reflection is the reflection of light from an uneven or granular surface such that an incident ray is seemingly reflected at a number of angles.
Radio waves
Radio waves are electromagnetic waves occurring within the portion of the electromagnetic spectrum which is a lower frequency than infrared radiation.
Refractive index
The refractive index of a medium is a measure for how much the speed of light is reduced inside the medium.
Snell's law
Snell's law is a formula used to describe the relationship between the angles of incidence and refraction for waves passing through a boundary between two different isotropic media.
Specular reflection
Specular reflection is the perfect, mirror-like reflection of light from a surface, in which light from a single incoming direction is reflected into a single outgoing direction.
Microwaves are a subcategory of radio waves with wavelengths shorter than one meter and longer than one millimeter.
Total internal reflection
Total internal reflection is an optical phenomenon that occurs when a ray of light strikes a medium boundary at an angle larger than the critical angle with respect to the normal to the surface.
Dispersion is the phenomenon that the phase velocity of a wave depends on its frequency.
Optical fiber
An optical fiber is a glass or plastic strand of material designed to guide light along its length.
A laser is a device that produces coherent radiation, typically in the form of a narrow, low-divergence beam and with a well-defined wavelength.
A retroreflector is a device that reflects a wave front back along a vector that is parallel to but opposite in direction from the angle of incidence.
Maxwell's equations
Maxwell's equations describe the interrelationship between electric field, magnetic field, electric charge, and electric current as well as the propagation of electromagnetic waves.
Fermat's principle
Fermat's principle or the principle of least time is the idea that the path taken between two points by a ray of light is the path that can be traversed in the least time.
Optical path length
Optical path length is the product of the distance of the path light follows through the system and the index of refraction of the medium through which it propagates.
Lambertian reflectance
A surface exhibits Lambertian reflectance when light falling on it is scattered such that the apparent brightness of the surface to an observer is the same regardless of the observer's angle of view.
James Clerk Maxwell
James Clerk Maxwell (1831 - 1879) was a Scottish mathematician and theoretical physicist whose set of equations in electricity, magnetism and inductance presented a unified model of electromagnetism and light.
Heinrich Hertz
Heinrich Rudolf Hertz (1857 - 1894) was the German physicist who demonstrated the existence of electromagnetic waves by building an apparatus to produce and detect UHF radio waves.
Cyclotron radiation
Cyclotron radiation is electromagnetic radiation emitted by moving charged particles deflected by a magnetic field.
Advanced terms that may appear in context in MCAT passages
Cauchy's equation
Cauchy's equation is an empirical relationship between the refractive index and wavelength of light for a particular transparent material.
Active laser medium
The active laser medium or gain medium is the material within a laser that exhibits optical gain.
Collimated light
Collimated light is light whose rays are parallel and thus has a planar wavefront
Snell's window
Snell's window is a phenomenon by which an underwater viewer sees everything above the surface through a cone of light of width around 100 degrees.
Optical cavity
An optical cavity or optical resonator is an arrangement of mirrors that forms a standing wave cavity resonator for light waves.
Lasing threshold
The lasing threshold is the lowest excitation level at which the laser's output is dominated by stimulated emission rather than by spontaneous emission.