Unit 7 Study Guide: Quantum Theory and Models

Photon

A discrete packet of energy representing a quantum of light.

Photoelectric Effect

The phenomenon where electrons are ejected from a metal surface when it is illuminated by light.

Planck's Constant (h)

A fundamental constant used to describe the sizes of quanta, approximately 6.63 x 10^-34 J·s.

Work Function (Φ)

The minimum energy needed to remove an electron from a metal surface.

Threshold Frequency (f₀)

The minimum frequency of light needed to eject electrons from a material.

Kinetic Energy (K_{max})

The maximum kinetic energy of ejected electrons, given by the equation K_{max} = hf - Φ.

Stopping Potential (V_s)

The reverse voltage needed to stop the flow of photoelectrons, equating to their kinetic energy.

De Broglie Wavelength

The wavelength associated with a particle's momentum, given by λ = h/p.

Macroscopic Objects

Large objects that do not exhibit wave-like behavior due to high momentum.

Microscopic Objects

Small particles, like electrons, whose behavior can demonstrate wave-like properties.

Electron Microscope

A device that uses accelerated electrons to achieve higher resolution imaging than optical microscopes.

Intensity of Light

The brightness or power per unit area of light; affects the number of ejected electrons but not their energy.

Frequency of Light

The number of oscillations of the light wave per unit time, directly related to the energy of individual photons.

Compton Scattering

A phenomenon where photons collide with electrons, demonstrating the particle nature of light.

Wave-Particle Duality

The concept that light exhibits both wave-like and particle-like properties depending on the experiment conditions.

Interference

The phenomenon where two or more waves overlap, resulting in a new wave pattern.

Diffraction

The bending of waves around obstacles and openings, demonstrating wave behavior.

Polarization

The orientation of light waves in particular directions, showcasing wave characteristics.

Electrons

Negatively charged subatomic particles that can exhibit wave-like behavior.

Energy (E)

The capacity of a physical system to perform work, related to the frequency of light in quantum physics.

Speed of Light (c)

A constant value representing the speed at which light travels in a vacuum, approximately 3.0 x 10^8 m/s.

Momentum (p)

The product of an object's mass and velocity, important in determining wave-like behavior.

Current in Photoelectric Effect

The flow of ejected electrons measured in response to light striking a metal surface.

Brighter Light Effect

Increasing light intensity results in more photons and hence more electrons ejected but does not increase their energy.

Negative Work Function (-Φ)

The y-intercept in a plot of K_{max} vs. Frequency, representing the work function of the metal.

Quantum Model of Light

The theory that light consists of quantized packets of energy (photons) rather than continuous waves.

Electromagnetic Radiation

A form of energy that is emitted and absorbed by charged particles, including light.

Young's Double Slit Experiment

An experiment demonstrating light's wave nature through interference patterns.