Exam 28: Quantum Physics

A photocathode that has a work function of 2.4 eV is illuminated with monochromatic light having photon energy 3.5 eV. What is the wavelength of this light? (c = 3.00 × 10⁸ m/s, h = 6.626 × 10^-34 J ∙ s, 1 eV = 1.60 × 10^-19 J)

When a metal is illuminated by light, photoelectrons are observed provided that the wavelength of the light is less than 520 nm. What is the metal's work function? (c = 3.00 × 10⁸ m/s, h = 6.626 × 10^-34 J ∙ s, 1 eV = 1.60 × 10^-19 J)

If the wavelength of a photon in vacuum is the same as the de Broglie wavelength of an electron, which one is traveling faster through space?

If a proton and an electron have the same speed, which one has the longer de Broglie wavelength?

A blue laser beam is incident on a metallic surface, causing electrons to be ejected from the metal. If the frequency of the laser beam is increased while the intensity of the beam is held fixed,

The electrons in a beam are moving at 18 m/s. (m_electron = 9.11 × 10^-31 kg, h = 6.626 × 10^-34 J ∙ s) (a) What is its de Broglie wavelength these electrons? (b) If the electron beam falls normally on a diffraction grating, what would have to be the spacing between slits in the grating to give a first-order maximum at an angle of 30° with the normal to the grating?

A photocathode having a work function of 2.8 eV is illuminated with monochromatic electromagnetic radiation whose photon energy is 4.0 eV. What is the threshold (cutoff) frequency for photoelectron production? (1 eV = 1.60 × 10^-19 J, h = 6.626 × 10^-34 J ∙ s)

Protons are being accelerated in a particle accelerator. When the energy of the protons is doubled, their de Broglie wavelength will

A metal surface has a work function of 2.50 eV. What is the longest wavelength of light that will eject electrons from the surface of this metal? (1 eV = 1.60 × 10^-19 J, c = 3.00 × 10⁸ m/s, h = 6.626 × 10^-34 J ∙ s)

A researcher is using x-rays to investigating a cubic crystal. He is looking at Bragg reflection from the planes parallel to the cube faces. He finds that when using x-rays with a wavelength of 0.165 nm, a strong first maximum occurs when the beam makes an angle of 23.5° with the planes. What is the spacing of adjacent atoms in this crystal?

If the de Broglie wavelength of an electron is 380 nm, what is the speed of this electron? (m_electron = 9.11 × 10^-31 kg, h = 6.626 × 10^-34 J ∙ s)

A beam of light with a frequency range from 3.01 × 10¹⁴ Hz to 6.10 × 10¹⁴ Hz is incident on a metal surface. If the work function of the metal surface is 2.20 eV, what is the maximum kinetic energy of photoelectrons ejected from this surface? (h = 6.626 × 10^-34 J ∙ s, 1 eV = 1.60 × 10^-19 J)

Electrons are accelerated to a speed of 4.0 × $10^4$ m/s and are then aimed at a double-slit apparatus, where interference fringes are detected. If the electrons were replaced by neutrons, what speed must neutrons have to produce interference fringes with the same fringe spacing as that observed with the electrons? (h = 6.626 × 10^-34 J ∙ s, m_electron = 9.11 × 10^-31 kg, m_neutron = 1.675 × 10^-27 kg)

A proton that is moving freely has a wavelength of 0.600 pm. (m_proton = 1.67 × 10^-27 kg, e = 1.60 × 10^-19 C, h = 6.626 × 10^-34 J ∙ s) (a) What is its momentum? (b) What is its speed? (c) What potential difference would it have been accelerated through, starting from rest, to reach this speed?

A person of mass 50 kg has a de Broglie wavelength of 4.4 × 10^-36 m while jogging. How fast is she running? (h = 6.626 × 10^-34 J ∙ s)

An 84-kW AM radio station broadcasts at 1000 kHz. How many photons are emitted each second by the transmitting antenna? (h = 6.626 × 10^-34 J ∙ s)

What is the longest wavelength of light that can cause photoelectron emission from a metal that has a work function of 2.20 eV? (1 eV = 1.60 × 10^-19 J, c = 3.00 × 10⁸ m/s, h = 6.626 × 10^-34 J ∙ s)

If the de Broglie wavelength of an electron is 2.4 μm, what is the speed of the electron? $\left( m \text { electron } = 9.11 \times 10 ^ { - 31 } \mathrm {~kg} , \right.$ $h = 6.626 \times 10^{ - 34} \mathrm {~J} \cdot \mathrm { s } )$

Two sources emit beams of microwaves. The microwaves from source A have a frequency of 10 GHz, and the ones from source B have a frequency of 20 GHz. This is all we know about the two beams. Which of the following statements about these beams are correct? (There could be more than one correct choice.)

A helium-neon laser emits light at 632.8 nm. If the laser emits $1.82 \times 10^{17}$ photons/second, what is its power output in mW? (c = 3.00 × 10⁸ m/s, h = 6.626 × 10^-34 J ∙ s)