AQA A-Level Physics 2.2 Electromagnetic Radiation and Quantum Phenomena Flashcards
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Questions and Answers

What happens when high voltage is applied across mercury vapor in a fluorescent tube?

  • Mercury atoms are excited and then return to the ground state, releasing UV photons.
  • The tube's phosphorus coating absorbs UV photons.
  • Fast-moving free electrons collide with the mercury atoms. (correct)
  • Mercury atoms cascade down energy levels and emit visible light photons.

    • Which process leads to the emission of visible light photons in a fluorescent tube?

  • Return of mercury atoms to the ground state
  • Absorption of UV photons by the phosphorus coating
  • Excitation of mercury electrons (correct)
  • Collision of free electrons with mercury atoms

    • What evidence supports the existence of discrete energy levels in atoms?

  • Variable emission wavelengths
  • Continuous emission spectra
  • Line emission and absorption spectra (correct)
  • Random absorption of photons

    • Which phenomenon states that all particles exhibit both wave and particle properties?

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

    In a fluorescent tube, what role does the phosphorus coating play?

    <p>Absorbing UV photons</p> Signup and view all the answers

    What triggers the emission of UV photons in a fluorescent tube?

    <p>Excitation of mercury atoms by absorbed UV photons</p> Signup and view all the answers

    Why do we observe lines at discrete points in line emission and absorption spectra?

    <p>Because electrons can only absorb an exact amount of energy</p> Signup and view all the answers

    What property of waves do particles exhibit according to wave-particle duality?

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

    How do line emission and absorption spectra relate to discrete energy levels in atoms?

    <p>They indicate where specific energy transitions take place in atoms.</p> Signup and view all the answers

    What happens to the electrons in a fluorescent tube's phosphorus coating after absorbing UV photons?

    <p>They are excited and cascade down energy levels.</p> Signup and view all the answers

    Study Notes

    Electromagnetic Waves

    • Electromagnetic waves are classified as transverse waves.

    Particle Behavior of Light

    • The photoelectric effect demonstrates the particle nature of light.

    Photoelectric Effect

    • Occurs when light above a specific frequency shines on metal, releasing electrons known as photoelectrons.

    Threshold Frequency

    • Defined as the minimum frequency of light necessary for an electron to be emitted from a metal surface.

    Photon Energy Calculation

    • The energy of a photon can be calculated using the equation E = hf = hc/λ, where:
      • E = energy
      • h = Planck’s constant
      • f = frequency
      • c = speed of light (3 x 10^8 m/s)
      • λ = wavelength

    Minimum Frequency Requirement

    • A photon must exceed a certain frequency for electron liberation, as its energy must surpass the work function (the energy needed to free an electron).

    Effects of Higher Frequency Photon

    • If a photon’s frequency is above the threshold, the electron is liberated, and any excess energy translates into the electron's kinetic energy.

    Effect of Increased Light Intensity

    • If photoelectric emission does not occur, increasing light intensity means more photons strike the metal, but unless the photon energy is sufficient, electron emission will not occur.

    Photoelectric Equation

    • The equation representing the photoelectric effect is given by:
      • Planck’s constant × frequency = work function + maximum kinetic energy of emitted photoelectrons.

    Work Function Definition

    • The work function is the energy required to free an electron from the metallic bonds holding it within a metal.

    Electron Volt Explanation

    • An electron volt (eV) is defined as the kinetic energy gained by an electron when accelerated through a potential difference of 1 volt.

    Conversion Between Electron Volts and Joules

    • To convert between electron volts and joules, use the conversion factor: 1 eV = 1.6 x 10^-19 joules.

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    Description

    Test your knowledge on electromagnetic radiation and quantum phenomena with these flashcards based on AQA A-Level Physics 2.2. Explore key concepts such as the nature of electromagnetic waves and quantum phenomena.

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