Interactive Quiz #4

This self-graded quiz consists of 10 questions (Part A of the 1996/97 Test 4). Answers are entered by clicking the option button corresponding to your selection. The quiz is graded by clicking the "Grade Quiz" button at the end of the quiz. Correct answers are found through hypertext links located at the end of the quiz.

1. Which of the following statements is true concerning the magnetic force on a charged particle in a magnetic field?
    (A) It is a maximum if the particle is stationary.
    (B) It is zero if the particle moves perpendicular to the field.
    (C) It is a maximum if the particle moves parallel to the field.
    (D) It acts in the direction of motion for a positively charged particle.
    (E) It depends on the component of the particle's velocity that is perpendicular to the field.
2. A proton travelling due east in a region containing only a magnetic field experiences a force which is directed vertically upwards. What is the direction of the magnetic field?
    (A) east
    (B) west
    (C) north
    (D) south
    (E) down
3. When electromagnetic waves travel through a vacuum, the various colours of visible light differ in
    (A) frequency only.
    (B) wavelength only.
    (C) speed only.
    (D) frequency and wavelength.
    (E) frequency and speed.
4. Consider a ray of light that passes from air into water. Which of the following statements is correct?
    (A) On entering the water the speed of the light decreases, with a corresponding decrease in frequency.
    (B) On entering the water the speed of the light increases, with a corresponding increase in frequency.
    (C) On entering the water the speed of the light decreases, with a corresponding decrease in wavelength.
    (D) On entering the water the speed of the light increases, with a corresponding increase in wavelength.
    (E) There is no change in speed when the light enters the water.
5. When a coin is viewed through a single lens, the image is seen to be upright and enlarged. Which of the following statements is correct?
    (A) The coin is located within the focal point of a converging lens (do < |f|).
    (B) The coin is located outside the focal point of a converging lens such that |f| < do < |2f|.
    (C) The coin is located outside the focal point of a converging lens such that do > |2f|.
    (D) The coin is located within the focal point of a diverging lens (do < |f|).
    (E) The coin is located outside the focal point of a diverging lens (do > |f|).
6. If you look carefully at an image formed in sunlight by a lens, you will observe chromatic aberration. This lens defect occurs because
    (A) rays that are farther from the optical axis are focused at a different position than those which are closer to the optical axis.
    (B) different wavelengths of light travel at different speeds through glass.
    (C) some wavelengths interfere constructively and others interfere destructively when they pass through the lens.
    (D) the lens creates a diffraction pattern similar to that produced by a circular aperture.
    (E) light is a transverse wave, rather than a longitudinal wave, like sound.
7. Photons of energy 6 eV cause electrons to be emitted from a certain metal with a maximum kinetic energy of 2 eV. Which of the following statements is true if photons of twice the wavelength are incident on the metal?
    (A) No electrons will be emitted.
    (B) Electrons will be emitted with a maximum energy of 1 eV.
    (C) Electrons will be emitted with a maximum energy of 4 eV.
    (D) Electrons will be emitted with a maximum energy of 8 eV.
    (E) Electrons will be emitted with a maximum energy of 10 eV.
8. The photon or 'particle' theory of electromagnetic radiation is necessary to explain the
    (A) refraction of light by a prism.
    (B) diffraction of light by a grating.
    (C) reflection of light by a mirrored surface.
    (D) results of Compton scattering experiments.
    (E) interference of light in Young's double-slit experiment.
9. The Bohr model of the hydrogen atom states that the electron orbits the nucleus with energy En, characterized by the quantum number n. The orbit radius
    (A) increases with increasing n.
    (B) decreases with increasing n.
    (C) remains the same when n changes.
    (D) decreases when the electron goes into a higher energy state.
    (E) is not related to n in any way.
10. Which of the following statements is true concerning the cutoff wavelength typically exhibited in X-ray spectra?
    (A) It depends on the target material.
    (B) It is independent of the energy of the incident electrons.
    (C) It depends on the potential difference across the X-ray tube.
    (D) It occurs when inner electrons are ejected from atoms in the target material.
    (E) It occurs because an incident electron cannot give up all its energy.
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Correct Answers

#1, #2, #3, #4, #5, #6, #7, #8, #9, #10
1. Which of the following statements is true concerning the magnetic force on a charged particle in a magnetic field?
    (E) It depends on the component of the particle's velocity that is perpendicular to the field.
Section 21.2 of the text.
2. A proton travelling due east in a region containing only a magnetic field experiences a force which is directed vertically upwards. What is the direction of the magnetic field?
    (C) north
Section 21.2 of the text - the Right Hand Rule.
3. When electromagnetic waves travel through a vacuum, the various colours of visible light differ in
    (D) frequency and wavelength.
Section 24.2 of text. In a vacuum, all electromagnetic waves travel at the same speed, so the various colours of light (which have different wavelengths) must also have different frequencies, since speed equals frequency times wavelength.
4. Consider a ray of light that passes from air into water. Which of the following statements is correct?
    (C) On entering the water the speed of the light decreases, with a corresponding decrease in wavelength.
Sections 26.1 and 26.2 of the text. Since the index of refraction of water is greater than that of air, the speed decreases when the light enters the water. Since the frequency of the light wave does not change, the wavelength of the light must also decrease.
5. When a coin is viewed through a single lens, the image is seen to be upright and enlarged. Which of the following statements is correct?
    (A) The coin is located within the focal point of a converging lens (do < |f|).
Section 26.7 of text. The only situation that produces an upright and enlarged image is for an object within the focal point of a converging lens.
6. If you look carefully at an image formed in sunlight by a lens, you will observe chromatic aberration. This lens defect occurs because
    (B) different wavelengths of light travel at different speeds through glass.
Sections 26.1, 26.5, and 26.14 of text. Chromatic aberration refers to the dependence of lens focal length on colour of light due to the dispersion of the light by the lens material. Dispersion is the dependence of refractive index, and therefore light speed, on the wavelength of the incident light.
7. Photons of energy 6 eV cause electrons to be emitted from a certain metal with a maximum kinetic energy of 2 eV. Which of the following statements is true if photons of twice the wavelength are incident on the metal?
    (A) No electrons will be emitted.
Section 29.3 of text. 6 eV photons causing emission of electrons with maximum kinetic energy of 2 eV means that the work function of the surface is 4 eV. Photons of twice the wavelength have half the energy, 3 eV. Therefore these photons do not have sufficient energy to overcome the work function and cause electron emission.
8. The photon or 'particle' theory of electromagnetic radiation is necessary to explain the
    (D) results of Compton scattering experiments.
Section 29.4 of text Wave theory cannot account for the change in wavelength that is observed in Compton scattering.
9. The Bohr model of the hydrogen atom states that the electron orbits the nucleus with energy En, characterized by the quantum number n. The orbit radius
    (A) increases with increasing n.
Section 30.3. The Bohr radius depends directly on the square of the quantum number.
10. Which of the following statements is true concerning the cutoff wavelength typically exhibited in X-ray spectra?
    (C) It depends on the potential difference across the X-ray tube.
Section 30.7 of text. The cutoff wavelength varies inversely with X-ray tube voltage (equation 30.17)

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