Electromagnetic Radiation and Quantum Theory
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Electromagnetic Radiation and Quantum Theory

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Questions and Answers

What is the frequency of the radiation calculated using a wavelength of $5800 \times 10^{-10}$ m?

  • 5.172 × 10<sup>14</sup> Hz (correct)
  • 219.3 m
  • 1.724 × 10^6 m<sup>-1</sup>
  • 1368 kHz

    • What does the value of 3.00 × 108 m s-1 refer to in the context of electromagnetic radiation?

  • Planck's constant
  • Wavelength of the radiation
  • Frequency of the radiation
  • Speed of light (correct)

    • What is the wavelength range of the visible spectrum mentioned in the content?

  • 600 nm to 900 nm
  • 1 nm to 50 nm
  • 400 nm to 750 nm (correct)
  • 200 nm to 300 nm

    • Which phenomenon can be explained by the wave nature of electromagnetic radiation?

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

    What does a wavelength of $5800 \times 10^{-10}$ m correspond to in centimeters?

    <p>1.724 × 10<sup>4</sup> cm</p> Signup and view all the answers

    What happens when light shines on a metal surface in the photoelectric effect?

    <p>Photoelectrons are ejected instantly from the metal.</p> Signup and view all the answers

    Which frequency is critical for observing the photoelectric effect for potassium metal?

    <p>$5.0 × 10^{14}$ Hz</p> Signup and view all the answers

    How does the number of ejected electrons relate to the light's intensity?

    <p>It is proportional to the intensity.</p> Signup and view all the answers

    What happens to the kinetic energy of ejected electrons as the frequency of light increases?

    <p>It increases.</p> Signup and view all the answers

    What factor determines the energy of a photon in the context of the photoelectric effect?

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

    What does the photoelectric effect demonstrate about particles of light?

    <p>They can be viewed as particles called photons.</p> Signup and view all the answers

    What is an incorrect statement about the photoelectric effect?

    <p>All metals have the same threshold frequency.</p> Signup and view all the answers

    What occurs when the frequency of the light is below the threshold frequency for a metal?

    <p>No photoelectrons are emitted.</p> Signup and view all the answers

    What is the relationship between the brightness of light and the number of electrons ejected?

    <p>The number of electrons ejected depends on the brightness of light.</p> Signup and view all the answers

    What does the kinetic energy of the ejected electrons depend on?

    <p>The frequency of the electromagnetic radiation.</p> Signup and view all the answers

    What does the term 'work function' refer to in this context?

    <p>The energy needed to eject an electron.</p> Signup and view all the answers

    According to the conservation of energy principle, how is the kinetic energy of the ejected electron calculated?

    <p>By subtracting work function from the total energy.</p> Signup and view all the answers

    What does the letter 'h' represent in the formula provided?

    <p>The Planck constant.</p> Signup and view all the answers

    Which light frequency is suggested to cause the ejection of electrons in the example given?

    <p>Red light.</p> Signup and view all the answers

    What is represented by $m_e$ in the equation provided?

    <p>The mass of the electron.</p> Signup and view all the answers

    Who is regarded as one of the two great physicists mentioned?

    <p>Albert Einstein.</p> Signup and view all the answers

    What is the equation used to calculate the kinetic energy of an emitted electron?

    <p>Kinetic energy = h(ν - ν0)</p> Signup and view all the answers

    What type of spectrum is produced by a substance that has absorbed energy?

    <p>Emission spectrum</p> Signup and view all the answers

    Which of the following correctly describes excited atoms, molecules, or ions?

    <p>They have absorbed radiation.</p> Signup and view all the answers

    What happens when a sample is heated or irradiated?

    <p>It emits energy as radiation.</p> Signup and view all the answers

    How is an absorption spectrum generated?

    <p>By passing a continuum of radiation through a sample.</p> Signup and view all the answers

    Which parameter in the equation Kinetic energy = h(ν - ν0) represents the threshold frequency?

    <p>ν0</p> Signup and view all the answers

    Which of the following statements about the speed of light is true?

    <p>It varies depending on the medium.</p> Signup and view all the answers

    What indicates a missing wavelength in an absorption spectrum?

    <p>A dark line in the spectrum.</p> Signup and view all the answers

    What occurs when a ray of white light passes through a prism?

    <p>It is spread out into a spectrum.</p> Signup and view all the answers

    Which type of spectrum includes dark spaces between bright lines?

    <p>Line spectrum</p> Signup and view all the answers

    Which property is restricted to discrete values known as quantization?

    <p>Energy levels</p> Signup and view all the answers

    What method was used to discover the element helium in the sun?

    <p>Emission spectroscopy</p> Signup and view all the answers

    How do atoms emit electromagnetic radiation in gaseous hydrogen?

    <p>During dissociation and energy excitation.</p> Signup and view all the answers

    What does the continuous spectrum of visible light represent?

    <p>A range of wavelengths from red to violet.</p> Signup and view all the answers

    What is the characteristic of emissions spectra of atoms in the gas phase?

    <p>They show only specific wavelengths with dark spaces.</p> Signup and view all the answers

    Which light color in the spectrum has the longest wavelength?

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

    Study Notes

    Electromagnetic Radiation

    • Frequency: The number of waves passing a point in one second (Hz)
    • Wavelength: The distance between two successive crests or troughs of a wave (m)
    • Speed of light (c): 3 x 10^8 m/s
    • Relationship between frequency and wavelength: c = νλ

    Particle Nature of Electromagnetic Radiation

    • Planck’s Quantum Theory: Energy is quantized, meaning it exists in discrete packets called quanta or photons.
    • Energy of a photon: E = hν, where h is Planck’s constant (6.626×10^-34 J s) and ν is the frequency.
    • Photoelectric Effect: Electrons are ejected from a metal surface when light shines on it.
      • Threshold frequency (ν0): Minimum frequency required for the photoelectric effect to occur.
      • Kinetic energy of ejected electrons: KE = hν - hν0 = hν - W0, where W0 is the work function.

    Atomic Spectra

    • Emission spectrum: The spectrum of radiation emitted by a substance that has absorbed energy.
      • Excited state: Atoms or molecules that have absorbed energy.
    • Absorption spectrum: The spectrum of radiation absorbed by a substance.
      • Line spectra or atomic spectra: Discrete bright lines emitted or absorbed by atoms in the gas phase due to transitions between quantized energy levels.
    • Spectroscopy: The study of emission or absorption spectra.
    • Line spectrum of hydrogen:
      • Energetically excited hydrogen atoms emit electromagnetic radiation at specific wavelengths.
      • The spectrum reveals the presence of quantized energy levels.

    Examples:

    • Helium (He) was discovered in the sun by spectroscopic methods.
    • When a ray of white light is passed through a prism, the wave with shorter wavelength bends more than the one with a longer wavelength.

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    Description

    This quiz covers key concepts in electromagnetic radiation, including frequency, wavelength, and the speed of light. It explores the particle nature of electromagnetic waves through Planck’s Quantum Theory and the photoelectric effect. Test your understanding of energy quantization and atomic spectra.

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