Modern Physics: Wave-Particle Duality of Light

Vocabulary practice flashcards covering wave-particle duality, historical developments, wave phenomena (reflection, refraction, dispersion, scattering, diffraction, interference), electromagnetism, and quantum mechanics.

Corpuscular Theory

The particle theory of light championed by Isaac Newton to explain the laws of reflection and refraction.

Ether

The hypothetical medium proposed by Robert Hooke through which light was believed to travel as a wave-like disturbance.

Wave-Particle Duality

The principle stating that light possesses both wave and particle characteristics; its propagation through space is governed by wave properties, whereas its energy exchange with matter is governed by particle properties.

Reflection

The process that occurs when a wave encounters a surface or barrier, is not absorbed, and bounces off the surface.

Law of Reflection

A fundamental rule of optics stating that the angle of incidence is equal to the angle of reflection.

Angle of Incidence ($i$)

The angle formed between the incoming incident ray of light and the normal line.

Angle of Reflection ($r$)

The angle formed between the reflected light ray and the normal line.

Normal Line

An imaginary reference line drawn perpendicular to a reflecting or refracting surface at the point of incidence.

Real Image

An optical image formed where light rays physically converge and intersect; it can be captured or projected on a screen.

Virtual Image

An optical image formed where light rays only appear to diverge from a point; it cannot be projected on a screen.

Inverted Image

An image orientation that appears upside down relative to the object.

Upright Image

An image orientation that maintains the same top-to-bottom orientation as the object.

Speed of Light (Ole Roemer's Measurement)

The measurement made in 1676 using astronomical observations of Jupiter's moon Io during eclipses, yielding a speed of $300{,}000{,}000\,\text{m/s}$.

Refraction

The bending of a light ray as it passes from one medium to another of different optical density, caused by a change in the speed of the wave.

Snell's Law

The law formulated in 1621 by Willebrord Snellius stating that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant: $n_1 \sin(\theta_1) = n_2 \sin(\theta_2)$.

Dispersion

The separation of white light into its full spectrum of constituent colors when passing through a prism or medium that refracts different wavelengths by different amounts.

Scattering

The deviation of light rays from a straight path in multiple directions caused by collisions with particles or molecules in a medium.

Diffraction

The bending and spreading out of light waves when passing through narrow openings, apertures, or around edges and obstacles.

Huygens' Principle

The principle proposed in 1678 stating that every point along a propagating wavefront acts as a source of secondary spherical wavelets; the tangent line envelope touching these wavelets constitutes the new wavefront.

Interference

The superposition of two or more overlapping light waves, creating reinforced constructive regions (bright bands) or canceling destructive regions (dark bands).

Electromagnetic Induction

The physical process discovered by Michael Faraday showing that a time-varying magnetic field induces an electric field.

Photons

Discrete, localized packets or quanta of energy that make up electromagnetic radiation, as identified in Albert Einstein's description of light.

Photon Energy Equation

The relationship $E = hf$, relating the energy of a single photon ($E$) directly to the frequency of light ($f$) via Planck's constant ($h$).

Photoelectric Effect

The phenomenon in which electrons are ejected from the surface of photosensitive metals (such as Cs, K, Na, Mg, and Ca) when light shines on them.

de Broglie Wavelength

The wave property attributed to matter by Louis de Broglie, defined by the formula $\lambda = \frac{h}{mv}$, indicating that moving particles exhibit wavelengths inversely proportional to their momentum.

Corpuscular Theory

The particle theory of light, utilized by Isaac Newton to explain the laws of reflection and refraction.

Ether

The hypothetical medium proposed by Robert Hooke through which light travels as a wave-like disturbance.

Christiaan Huygens

A Dutch physicist and mathematician who championed the wave theory of light, explaining refraction as material-dependent propagation and proposing that every point on a wavefront acts as a source of secondary wavelets.

Thomas Young

One of the primary proponents of the wave theory of light, which explained refraction through the material-dependent propagation of light particles.

James Clerk Maxwell

An English physicist who advanced optical theory by formulating the theory of electromagnetism and mathematically demonstrating that light is a form of electromagnetic radiation.

Photons

Packets of energy comprising light, introduced by Albert Einstein through the photoelectric effect, where each packet carries energy proportional to the frequency of light ($E = hf$).

Wave-Particle Duality

The principle stating that light exhibits both wave and particle characteristics, where wave properties describe light propagation and particle properties govern energy exchange with matter.

Reflection

The wave phenomenon that occurs when a wave strikes a barrier or surface without being absorbed and bounces off.

Law of Reflection

The optical principle stating that the angle of incidence is equal to the angle of reflection ($i = r$).

Angle of Incidence ($i$)

The angle formed between the incoming incident light ray and the normal line.

Normal Line

An imaginary reference line drawn perpendicular to a surface at the point of incidence.

Angle of Reflection ($r$)

The angle formed between the reflected light ray and the normal line.

Real Image

An image formed when light rays physically intersect, allowing it to be projected onto a screen.

Inverted Image

An optical image that is upside down relative to the object's actual orientation.

Virtual Image

An image formed where light rays only appear to diverge from a common point, meaning it cannot be captured on a screen.

Upright Image

An image that maintains the identical vertical orientation as the original object.

Galileo Galilei

The scientist who made the first attempt to measure the speed of light using lanterns on hilltops, which was unsuccessful due to the extremely fast time-lapse.

Ole Roemer

The astronomer who made the first true measurement of the speed of light in 1676, calculating a value of $300{,}000{,}000\,\text{m/s}$ using eclipse timings of Jupiter's moon, Io.

Refraction

The change in direction of light as it passes between media of differing optical densities, caused by a change in the speed of the wave.

Snell's Law

The optical law formulated in 1621 by Willebrord Snellius establishing that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant ($n_1 \sin(\theta_1) = n_2 \sin(\theta_2)$).

Dispersion

The separation of white light into its full spectrum of constituent colors when traveling through a prism or medium that refracts wavelengths at different angles.

Scattering

The process where light or other electromagnetic radiation is forced to deviate from a linear path and radiate in various directions due to particles or irregularities in the medium.

Diffraction

The spreading and bending of light waves around obstacles or through narrow slits rather than traveling in pure straight lines.

Huygens' Principle

The wave principle established in 1678 proposing that every point along a wavefront acts as an individual emitter of secondary wavelets, creating the next wavefront along their common tangent.

Interference

The phenomenon occurring when overlapping light waves superimpose to produce a combined wave pattern, forming bright areas (constructive) and dark areas (destructive).

Hans Christian Oersted

A Danish scientist who demonstrated the link between electricity and magnetism by discovering that electric currents generate magnetic fields.

Andre-Marie Ampere

A French physicist who discovered that a current-carrying wire loop produces an surrounding magnetic field directed according to the current flow.

Michael Faraday

An English physicist who discovered electromagnetic induction, revealing that a changing magnetic field induces an electric field.

Heinrich Hertz

A German physicist who experimentally confirmed the reality of electromagnetic waves in the late 1880s, confirming that light is a high-frequency electromagnetic wave.

Photoelectric Effect

The emission of electrons from photosensitive metals (such as $\text{Cs}$, $\text{K}$, $\text{Na}$, $\text{Mg}$, and $\text{Ca}$) when exposed to incident light.

Louis de Broglie

A French physicist who proposed that all physical matter exhibits wave characteristics, possessing a wavelength related to Planck's constant divided by momentum.

de Broglie Wavelength

The wave property associated with any moving particle ($\lambda = \frac{h}{mv}$), which is inversely proportional to momentum such that faster or heavier particles have shorter wavelengths.