Modern Physics Vocabulary

Flashcards about Modern Physics.

Matter

Anything that occupies some space (volume) and has mass; composed of atoms.

Mass

The amount of stuff that makes up an object.

Energy

The ability to do work or produce heat.

Work

Process of moving an object.

Heat

Energy that is transferred from an object with a higher temperature to an object with a lower temperature.

Particles & waves

Represent the only modes of energy transport (interaction) between two points.

MATTER (PARTICLES)

Complete localized.

WAVES

Cannot be confined to any particular region of space. A wave can be “simultaneously everywhere” at a given instance in time.

Energy carried by a particle

Energy is concentrated in it & is not spreading over the boundary that defines its physical location. energy of a particle is corpuscular (discrete)

Energy carried by wave

Energy spreads over an infinite region of space along the direction the wave propagates. energy is distributed spread all over the space in a continuous manner

Waves

Waves undergo diffraction and interference.

Electromagnetic (EM) wave

A traverse wave that is a transfer of electric and magnetic energy.

Waves

Waves undergo diffraction and interference.

EM radiation

The energy that EM waves transfer.

REFLECTION

A phenomenon where light waves bounce off a surface.

REFRACTION

The bending of light as it passes from one medium to another.

DIFFRACTION

The spreading of waves as they pass through an opening or around an obstacle.

INTERFERENCE

The combination of two or more waves to form a resultant wave of greater or lower amplitude.

POLARIZATION

A phenomenon where transverse waves are filtered based on their direction of oscillation.

Amplitude (A)

The vertical distance between the tip of a crest and the wave’s central axis; associated with the brightness, or intensity, of the wave.

Wavelength (𝛌)

The horizontal distance between two consecutive troughs or crests of a wave.

Frequency (f)

The number of full 𝛌s that pass by a given point in space every second; the SI unit is Hertz (Hz).

Hertz

Discovered the photoelectric (PE) effect → when light above a critical frequency hits a metal surface, e- s are releases.

Blackbody

An ideal body that completely absorbs all the radiations incident on it from all angles.

Blackbody radiations

Radiation emitted by a black body.

Intensity (I)

Total radiated power (P) per unit area (A) (unit: Watt/m2)

Radiance (R)

The power radiated per unit area (intensity) per unit wavelength interval (𝛌+d𝛌) (at a given wavelength, 𝛌 & temperature, T) (unit: Watt/m2/m).

Energy density (u)

The total energy per unit volume in the cavity in the frequency interval between f and f + df (unit: J/m3)

Emissivity (e)

The ratio of the total emissive power of the body to the total emissive power of a black body.

Stefan-Boltzmann’s Law (1879)

Concerns the total power of blackbody radiation emitted across the entire spectrum of wavelengths at a given temperature. 𝑃 = 𝜎𝐴𝑒𝑇4

Wien’s Displacement Law (1893)

States that the blackbody radiation curve for different T will have different peaks at different 𝛌 & inversely proportional to T (as the T of the body increases, the 𝛌 at the emission peak decreases).

Rayleigh-Jeans (R-J) Law

The classical physics predicted that as the f of radiation increases, the energy emitted would increase too. R(𝜆, 𝑇) = 2𝜋𝑐𝑘𝐵𝑇/𝜆4

Planck’s Law

The total EM radiation absorbed & emitted/radiated by a body is not emitted continuously but is made up of discrete units @ quanta of energy (E).