PHYSICS 111(02): QUIZ 06

Answers are at bottom of page.

  1. A beam of light consists of 600 nm orange light and 400 nm violet light. The beam strikes a diffraction grating at normal incidence (angle of incidence = 0). Which of the following statements is correct?

  2. Consider a beam of red light and a beam of blue light travelling through a vacuum:

  3. A metal surface is illuminated with light of a particular frequency, and photoelectrons are ejected. The light source is now adjusted so that the light is of higher intensity (but same frequency). The result when the metal surface is illuminated with this higher intensity light is:

  4. Compton studied the scattering of X-rays from a graphite target. He observed that

  5. When a hydrogen atom makes the transition from the n = 3 state to the n = 2 state

  6. Which of the following statements correctly describes the result of increasing the voltage applied across an X-ray tube?

  7. Laser light is produced by a process called:

  8. If a nucleus containing A nucleons has a radius of r, then a nucleus containing 8A nucleons has a radius of approximately:

  9. Which of the following statements regarding the strong nuclear force is TRUE?

  10. The radioactive decay of 3617Cl to 3618Ar is an example of:

 

ANSWERS:

  1. (D) - From the equation for the locations of interference maxima, , the angles of the maxima depend on the product of the order, m, and the wavelength, . Therefore, the orange 2nd order maximum occurs at the same angle as the violet 3rd order maximum since 2×(600 nm) equals 3×(400 nm).
  2. (C) - The wavelength of red light is about 700 nm and that of blue light is about 450 nm. (Speed, c, is the same for all e-m radiation propagating in a vacuum; frequency and photon energy are inversely related to wavelength, )
  3. (A) - Same frequency of light means that the photon energy is unchanged and therefore so is the maximum electron kinetic energy unchanged (hf = KEmax + Wo). Higher intensity of light means more photons per unit time are striking the metal surface and therefore electrons will be ejected at a greater rate.
  4. (B) - X-rays scattering from electrons in the target have larger wavelengths (lower energy) due to transfer of energy to the electrons. (Compton equation is obtained by applying conservation of linear momentum and energy to the photon-electron 'collision'.)
  5. (C) - A lower quantum number means a lower energy state. The difference in energy is carried away by the emitted photon.
  6. (E) - The K-alpha peak wavelength is a property of the tube anode material and does not depend on the applied tube voltage. Since the maximum X-ray energy depends directly on the applied tube voltage and X-ray wavelength is inversely related to X-ray energy, the minimum X-ray wavelength decreases with an increase in tube voltage.
  7. (A)
  8. (A) - Since nuclear radius varies as the cube root of the mass number, and the cube root of 8 is 2, the nucleus with mass number 8 will have a radius of approximately 2r.
  9. (E) - The strong nuclear force is very short-ranged, each nucleon only feeling the strong nuclear attraction due to its 'nearest neighbours'.
  10. (A) - Since the nucleon number of the daughter is the same as that of the parent, this cannot be alpha decay. Since the atomic number of the daughter is one greater than that of the parent, the charge of the decay particle must be -1e. The particle with mass number 0 and charge of -e is the electron, so this is an example of beta- decay.

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