U4T2: QUANTUMMECHANICS

When objects are heated up they emit electromagnetic waves (light) of a specific colour that corresponds with their temperature. The spectrum of radiation emitted by a black body is called blackbody radiation. A perfect black body is an object that emits everything it absorbs. Examples of blackbodies are stars and blackholes.

A problem with the classical theory of blackbody radiation was that at ultraviolet wavelengths the peak intensity would approach infinity. This was clearly wrong and was called the ultraviolet catastrophe which meant the classical theory was wrong.

The interference pattern produces when light passes through the two slits provides evidence that light has the properties of a waves, as it resembles the same pattern produces by mechanical waves.

<p>Light is a type of wave called an electromagnetic wave. Electromagnetics waves are created by the process of oscillation (when electric charges move back and forth). When oscillation occurs 2 types of fields are generated, an electric field and a magnetic field. These two fields move perpendicular to each other.</p> Signup and view all the answers

<p>When an object such as a hollow metal block is heated, radiation is emitted and is assumed to come from the particles inside the block. This is the concept of black body radiation. The thermal agitation of the the particles making up the black body results in radiation being emitted. The intensity and wavelength of the radiation must come from the vibrations of the particles. The only way to explain the particular shape of the distribution curve is to assume the radiation is emitted in discrete bundles of energy called quanta or photons. Hence, the concept of black body radiations is that heating a black body produced radiation whose characteristics can only be explained in terms of the emission of light quanta.</p> Signup and view all the answers

<p>Photons are discrete packets of energy of electromagnetic waves.</p> Signup and view all the answers

<p>The photoelectric effect is the phenomena of electrons being emitted from a material when photons strike it.</p> Signup and view all the answers

<p>Threshold frequency is the minimum frequency of a photon that can eject an electron from a surface, measure in hertz (Hz). Each surface has a different threshold frequency. This means that even when the light shining on the material is intense it will not cause the electron to be ejected until it reaches the threshold frequency for that material.</p> Signup and view all the answers

<p>Planck's constant is a fundamental constant used in quantum mechanics that relates frequency to energy (h).</p> Signup and view all the answers

<p>Work function (W) is the minimum energy required to remove an electron from a solid, measured in joules (J) or electron volts (eV).</p> Signup and view all the answers

<p>Rutherford's model of the atom is a small, central, positively charged nucleus with negatively charges electrons orbiting around it. Rutherford's did not account for the stability of atoms and the emission lines in the hydrogen spectrum.</p> Signup and view all the answers

<p>Bohr explained that electrons can move between the said discrete level by an addition of energy, as the electron moves back to its ground state it emits a photon, emitting a specific wavelength of radiation, drawing a line that corresponds to the hydrogen line spectrum.</p> Signup and view all the answers

<p>Rutherford described the atom as consisting of tiny positive masses surrounded by a cloud of electrons. Bohr thought the electrons orbited the nucleus in quantised orbits. This built upon Rutherford's model so it was not possible for electrons to occupy just any energy level.</p> <p>OR</p> <p>The Bohr model of the atom demonstrates that electrons exist in discrete energy levels, ultimately addressing Rutherford's model - that was limited in that it did not take into account the stability of the atom. Bohr also described that electrons can jump between energy levels, describing the emission spectrum.</p> Signup and view all the answers

<ol> <li>Blackbody radiation since the radiation that occurs is due to vibrations of particles. 2) Photoelectric (PE) effect since this phenomenon could only be explained by the quantization of light. 3) Compton effect</li> </ol> Signup and view all the answers

<p>Young's double slit experiment, specifically the diffraction and interference that occurs.</p> Signup and view all the answers

<p>Electrons in atoms exit in stationary states. Transition between stationary states involves absorption or emission of electromagnetic radiation. Angular momentum of a stationary electron is quantised.</p> Signup and view all the answers