Quantum Physics

Surface of a metal is irradiated with UV radiation, λ = 100 nm. Work function is w_e = 6.9 eV. What is the de Broglie wavelength of the emitted photoelectrons? Presume that the energy of a photon is converted without losses to electron energy. (h = 6.63 × 10⁻³⁴ Js, m_e = 9.11 × 10⁻³¹ kg, 1.0 eV = 1.60 × 10⁻¹⁹ J)

• 0.05 nm

• 0.52 nm

• 5.22 nm

• 52.2 nm

• 522 nm

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A light-emitting diode emits red light of wavelength 6.4 × 10⁻⁷ m. Calculate the energy of photon of the red light .

a the frequency of the red light

• 1.94 eV

• 19.4 eV

• 31.1 eV

• 3.11 eV

• 4.97eV

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Lithium atoms emit red light of wavelength 670 nm. Determine the difference between the energy levels responsible for this red light.

• 18.6 eV

• 1.86 eV

• 2.97 eV

• 0.30 eV

• 0.19 eV

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An electron in an atom can occupy four (4) energy levels. What is the maximum number of spectral emission lines from this atom?

• 4

• 5

• 6

• 7

• 8

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An electron is accelerated through a potential difference of 6.0 V. According to a student, this electron has kinetic energy greater than the energy of a photon of ultraviolet radiation of wavelength 2.5 × 10⁻⁷ m. Determine the kinetic energy of a photon of UV radiation.

• 79.6×10⁻¹⁹ J

• 0.80×10⁻¹⁹ J

• 0.08×10⁻¹⁹ J

• 7.96×10⁻¹⁹ J

• 796×10⁻¹⁹ J

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What is the energy level of the ground state (n = 1) and the energy level of the first excited state (n = 2).

• E₁= –2.18 × 10⁻¹⁸ J & E₂ = -5.45 × 10⁻¹⁹ J

• E₁= –5.45 × 10⁻¹⁸ J & E₂ = -2.18 × 10⁻¹⁹ J

• E₁= –21.8 × 10⁻¹⁸ J & E₂ = 54.5 × 10⁻¹⁹ J

• E₁= –54.5 × 10⁻¹⁸ J & E₂ = -21.8 × 10⁻¹⁹ J

• E₁= –545 × 10⁻¹⁸ J & E₂ = -218 × 10⁻¹⁹ J

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Calculate the wavelength of radiation emitted when an electron makes a transition from the first excited state to the ground state. In which region of the electromagnetic spectrum would you find a spectral line with this wavelength.

• 1.22×10⁻⁸ m gamma ray

• 1.22×10⁻⁷ m x - ray

• 1.22×10⁻⁵ m Infrared

• 1.22×10⁻⁶ m Visible light

• 1.22×10⁻⁷ m UV

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A metal is illuminated by visible light of different wavelengths. A photoelectron has a maximum kinetic energy of 0.9 eV when red light of wavelength 640 nm is used. With blue light of wavelength 420 nm, the maximum kinetic energy of the photoelectron is 1.9 eV. Find the experimental value for the Planck constant h. (in 2 s.f)

(a)  

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Neutrons travelling through matter get diffracted just as electrons do when travelling through graphite. In order to show diffraction effects, the neutrons need to have a

de Broglie wavelength that is comparable to the spacing between the atoms. Determine the speed of a neutron that has a de Broglie wavelength of 2.0 × 10⁻¹¹ m. Express your answer in 3 s.f

(a)  

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Determine the accelerating p.d. V that gives an electron a de Broglie wavelength of 4.0 × 10⁻¹¹ m.

(a)  

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