Photon Model and Planck's Constant Quiz
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Questions and Answers

What does the photoelectric equation ℎ𝑓𝑓 = 𝜙𝜙 + 𝐾𝐾𝐾𝐾𝑚𝑎𝑎𝑥𝑥 imply about the energy of the incident photon?

  • It is only considered if the intensity is high.
  • It is equal to the work function plus the maximum kinetic energy of the emitted electron. (correct)
  • It is less than the work function of the metal.
  • It is independent of the work function.
  • What determines whether electrons will be released from a metal's surface?

  • The frequency of the incident radiation. (correct)
  • The temperature of the metal.
  • The intensity of the incident radiation.
  • The duration of exposure to light.
  • Which effect occurs when increasing the intensity of radiation above the threshold frequency?

  • Decrease in the wavelength of the incident radiation.
  • Increase in the number of emitted electrons. (correct)
  • Increase in the kinetic energy of each electron.
  • Decrease in the work function of the metal.
  • What is the relationship described by the de Broglie equation?

    <p>Wavelength is inversely proportional to momentum.</p> Signup and view all the answers

    In the context of the photoelectric effect, what does the threshold frequency represent?

    <p>The minimum frequency required to release electrons.</p> Signup and view all the answers

    How does increasing the mass of a particle affect its observable wave properties?

    <p>The wavelength decreases, making wave properties harder to observe.</p> Signup and view all the answers

    If the energy of the incoming photon is exactly equal to the work function, what is the expected outcome?

    <p>Electrons are emitted with zero kinetic energy.</p> Signup and view all the answers

    What is the implication of wave-particle duality in relation to light?

    <p>Light can exhibit both wave-like and particle-like properties depending on the experiment.</p> Signup and view all the answers

    What happens to the gold leaf in an electroscope when UV light is shone on the zinc plate?

    <p>The gold leaf falls as negative charge is lost.</p> Signup and view all the answers

    Why does visible light not cause electrons to be released from the zinc plate?

    <p>Electrons require energy above the work function to escape.</p> Signup and view all the answers

    What is the work function in the context of the photoelectric effect?

    <p>The minimum energy required to free an electron from the surface of a metal.</p> Signup and view all the answers

    What is the relationship between the frequency of a photon and its energy?

    <p>Energy is directly proportional to frequency.</p> Signup and view all the answers

    What is the effect of increasing the intensity of visible light on the photoelectric effect?

    <p>It has no effect on electron release.</p> Signup and view all the answers

    Which electromagnetic radiation is capable of producing the photoelectric effect on a metal?

    <p>Ultraviolet light</p> Signup and view all the answers

    What can be concluded from the observation that electrons are released instantaneously when UV light is used?

    <p>Photons of UV light have high enough energy to immediately overcome the work function.</p> Signup and view all the answers

    How does excess energy from a photon impact a released electron?

    <p>It becomes kinetic energy of the electron.</p> Signup and view all the answers

    What is the relationship between the energy of a photon and its frequency?

    <p>Energy is directly proportional to frequency.</p> Signup and view all the answers

    Which of the following is a correct definition of an electronvolt?

    <p>The energy transferred when an electron travels through a potential difference of 1 volt.</p> Signup and view all the answers

    What is the purpose of using a potential divider in the experiment with LEDs?

    <p>To vary the voltage applied across the LED.</p> Signup and view all the answers

    How is the value of Planck's constant estimated using LEDs?

    <p>By determining the threshold potential difference and the wavelength of the emitted light.</p> Signup and view all the answers

    In the experiment setup with LEDs, what does the gradient of the graph of V against 1/λ represent?

    <p>The value of Planck's constant multiplied by the speed of light.</p> Signup and view all the answers

    Which of the following statements about photons is incorrect?

    <p>The energy of a photon is constant regardless of its frequency.</p> Signup and view all the answers

    When conducting experiments with different colored LEDs, what is being varied?

    <p>The wavelength of emitted light.</p> Signup and view all the answers

    What does the term 'threshold p.d.' refer to in the context of LEDs?

    <p>The minimum voltage required for the LED to emit light.</p> Signup and view all the answers

    Study Notes

    The Photon Model

    • Electromagnetic radiation exhibits wave-like properties such as diffraction and interference.
    • When interacting with matter, electromagnetic radiation behaves as discrete energy packets called photons.
    • The energy of a photon is directly proportional to its frequency.
    • The relationship between energy (E), frequency (f), and wavelength (λ) of a photon is defined by the equation E = hf = hc/λ, where h is Planck's constant (6.63 x 10^-34 Js).
    • The electronvolt (eV) is a more convenient unit for photon energy than joules, with 1 eV = 1.60 x 10^-19 J.

    Determining Planck's Constant using LEDs

    • LEDs emit light only when the applied voltage exceeds a specific threshold value.
    • Measuring the threshold voltage and the wavelength of light emitted by different LEDs can be used to estimate the Planck constant.
    • By plotting a graph of threshold voltage (V) against 1/λ, the gradient is equal to hc/e.
    • From the gradient, Planck's constant (h) can be calculated.

    The Photoelectric Effect

    • The photoelectric effect occurs when electromagnetic radiation is incident on a metal surface, causing the release of electrons.
    • Electrons only escape from the metal surface if the incident light has a frequency equal to or greater than the threshold frequency for the specific metal.
    • Each photon can transfer its energy to a single electron, with any excess energy beyond the work function appearing as the electron's kinetic energy.
    • The work function (ϕ) is the minimum energy required for an electron to escape the metal surface.
    • The maximum kinetic energy (KEmax) of the released electron is determined by Einstein's photoelectric equation: hf = ϕ + KEmax.

    Wave-Particle Duality

    • The photoelectric effect suggests a particulate nature of light while diffraction and interference demonstrate its wave-like behavior.
    • This duality is called wave-particle duality, implying that electromagnetic radiation has both wave and particle characteristics.
    • De Broglie proposed that all matter exhibits wave-particle duality.
    • The De Broglie equation relates the wavelength (λ) of a particle to its momentum (p): λ = h/p = h/mv.
    • This equation highlights that the wavelength of a particle decreases as its mass increases, making wave-like behavior harder to observe for larger particles.

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    Description

    Explore the concepts of electromagnetic radiation and the photon model in this quiz. You will learn about the wave-like properties of light, the energy of photons, and how to determine Planck's constant using LEDs. Test your knowledge on these fundamental principles of physics!

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