Fundamentals of Light and Matter Interaction
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Questions and Answers

What does the Bohr model primarily demonstrate about electrons?

  • Electrons do not follow specific paths around the nucleus.
  • Electrons are located in a probability cloud surrounding the nucleus.
  • Electrons can exist at varying distances from the nucleus with distinct energy levels. (correct)
  • Electrons can be created or annihilated in the atomic structure.
  • Which phenomenon is associated with phenomena such as blackbody radiation and the photoelectric effect?

  • Quantum Mechanics. (correct)
  • Alternating current.
  • Thermodynamics.
  • Classical Mechanics.
  • What is the formula used to calculate the energy of a photon?

  • E=mc^2
  • E=1/2mv^2
  • E=hf (correct)
  • E=hv^2
  • What does fluorescence refer to in the context of molecular interactions?

    <p>Absorption and subsequent re-emission of light by excited molecules.</p> Signup and view all the answers

    Which scattering technique is characterized by inelastic scattering of photons?

    <p>Raman scattering.</p> Signup and view all the answers

    Which type of energy is not categorized under molecular energies?

    <p>Magnetic energy</p> Signup and view all the answers

    What is the minimum point of the molecular potential energy curve referred to as?

    <p>Equilibrium bond length Re</p> Signup and view all the answers

    How many normal vibrational modes does a diatomic molecule have?

    <p>2</p> Signup and view all the answers

    Which of the following describes the vibrational modes of a nonlinear molecule?

    <p>3N-6 vibrational modes</p> Signup and view all the answers

    What determines the finite number of quantized vibrational energy states?

    <p>Bond disassociation energy Do</p> Signup and view all the answers

    Which of these types of motions does not fall under molecular energies?

    <p>Torsional</p> Signup and view all the answers

    Which of the following statements about quantized effects is true?

    <p>They influence both electronic and vibrational energies.</p> Signup and view all the answers

    For a molecule with N atoms, how many vibrational modes does it have if it is characterized as linear?

    <p>3N-5</p> Signup and view all the answers

    What was a key contribution of de Broglie in 1924 to quantum mechanics?

    <p>Wave-particle duality of matter</p> Signup and view all the answers

    In the context of quantum mechanics, how are electrons described in terms of energy?

    <p>By quantized energy levels</p> Signup and view all the answers

    Which of the following correctly describes the relationship between mass and wavelength for a particle?

    <p>Wavelength varies inversely with mass of the particle</p> Signup and view all the answers

    What distinguishes isotopes of the same element?

    <p>Different neutron counts</p> Signup and view all the answers

    What is the shape of the 2p orbital in atomic structure?

    <p>Dumbbell-shaped</p> Signup and view all the answers

    Which condition leads to the emission of spectral bands in the hydrogen atom?

    <p>Radiative electron transitions</p> Signup and view all the answers

    What defines the kinetic energy equation for a particle?

    <p>$mv^2$ divided by 2</p> Signup and view all the answers

    How many electrons can the 3s orbital accommodate?

    <p>6</p> Signup and view all the answers

    Study Notes

    Module Structure

    • The module covers fundamental concepts of light, propagation in waveguides, and light's interaction with matter.
    • Topics include lasers, photobiology basics, biophotonics applications (bioimaging, tissue engineering), and more.

    Topics to be Covered

    • Atoms and Molecules
      • Molecular interactions including absorption, spontaneous and stimulated emission.
      • Fate of excited molecules, specifically fluorescence.
      • Light scattering phenomena like Rayleigh, Mie, and Raman spectroscopy.

    At the Start

    • The atom was considered an indivisible particle.
    • Atoms combine to form different elements.
    • Early models of the atom, such as the "plum pudding" model, were proposed.

    Failures of Classical Mechanics

    • Classical mechanics failed to explain phenomena like blackbody radiation, photoelectric effect, and discrete emission bands.
    • Quantum mechanics was developed to address these failures.

    Quantization of Energy

    • Max Planck proposed that energy is quantized in whole multiples.
    • Einstein's explanation of the photoelectric effect further supported the concept of quantized energy.
    • Planck's constant (6.626068 × 10⁻³⁴ m² kg / s) is a crucial constant in quantum mechanics.

    Rutherford Model

    • A "planetary" model, with electrons orbiting a nucleus containing protons and neutrons.
    • The model depicts electrons in orbit around the nucleus.

    Bohr Model (1913)

    • The Bohr model describes electrons orbiting the nucleus at specific distances.
    • Electrons occupy different energy levels.
    • Radiation is emitted or absorbed when electrons transition between energy levels.
    • Different shells hold different numbers of electrons (1st shell = 2, 2nd shell = 8, and 3rd shell = 18).

    Electron Transitions

    • Electrons can absorb or emit photons during transitions between energy levels.
    • Energy of transition is equal to the energy of the absorbed or emitted photon.
    • Photon emission, energy of the photon, discrete energy, and spectroscopy are related aspects of electron transitions.

    Quantum Mechanics Model

    • De Broglie proposed that particles can have wave-like properties.
    • Schrödinger's wave equations describe the behavior of electrons in an atom.
    • Electrons occupy orbitals that have specific shapes and energies.
    • At higher energies, electron orbitals have complex shapes.

    Wave-Particle Duality of Matter

    • Matter exhibits both particle and wave characteristics.
    • Kinetic energy and momentum are particle-like properties.
    • Wavelength and quantized energy are wave-like properties.

    Parts of the Atom

    • Atoms consist of electrons, protons, and neutrons.
    • Electrons are negatively charged, protons are positively charged, and neutrons have no charge.
    • The mass of an electron is much smaller than the mass of a proton or neutron.
    • The number of electrons equals the number of protons in a neutral atom.
    • Isotopes have different numbers of neutrons.
    • An "ion" is an atom with an unequal number of electrons and protons (charged).

    Filling Orbitals with Electrons

    • Electrons fill atomic orbitals in a specific order, following the Aufbau principle.
    • Subshells (s, p, d, f) and shells (n=1, 2, 3...) are distinct energy levels.
    • Electrons occupy different orbitals in a specific order to achieve the lowest energy configuration.

    Orbital Shapes

    • Different atomic orbitals have different shapes (1s, 2s, 2p, 3s, 3p, 3d).

    Allowed Transitions in the Hydrogen Atom

    • Hydrogen atom transitions demonstrate discrete energy levels and specific spectral emission bands.
    • The allowed transitions between energy levels generate specific wavelengths of light which can be mapped in spectral emission bands.

    Molecular Energies

    • Molecules have various forms of energy (electronic, vibrational, rotational and translational).
    • Quantized effects are observed in all energies levels.
    • Rotation and vibration contribute to molecular properties.

    Molecular Potential Energy Curve

    • A curve detailing energy changes with internuclear separation (distance between nuclei).
    • Equilibrium bond length (minimum on the curve) represents the most stable distance.
    • The minimum point on the curve indicates the molecule's most stable bond state.

    Molecular Vibrational States

    • Molecular vibrations are quantized, leading to specific vibrational energy levels.
    • Bond dissociation energy (maximum energy to break a bond) is a critical parameter.
    • Finite number of quantized vibrational energy states determines the vibrational modes.

    Typical Normal Vibrational Modes

    • Molecules have specific vibrational modes (e.g., symmetric, asymmetric, bending).
    • Linear molecules (3N-5) and non-linear molecules (3N-6) have different numbers of vibrational modes depending on their geometry.

    Summary

    • Energy is absorbed and emitted in discrete quanta (packets).
    • Quantum mechanics describes electron orbitals and their shapes.
    • Electrons can transition between energy levels, emitting or absorbing photons.
    • Molecular bonds vibrate with quantized energies, affecting their behavior.

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    Description

    This quiz explores the fundamental concepts of light, its propagation in waveguides, and interactions with matter. Topics include lasers, molecular interactions, and the principles of photobiology and biophotonics applications. Test your understanding of atomic theories and the transition from classical mechanics to quantum mechanics.

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