Question 1

Which experiment provided the first direct measurement of the charge of the electron, and what was the key finding?

Accepted Answer

Millikan's oil drop experiment, which showed that the charge was always an integral multiple of a smallest charge $$e$$

Question 2

According to Planck’s quantum hypothesis, what is the quantized energy of an atomic oscillator with frequency $$f$$?

Accepted Answer

The energy is $$E = n h f$$, where $$n is an $$integer and $$h is $$Planck's constant

Question 3

Which observation about the photoelectric effect cannot be explained by classical wave theory?

Accepted Answer

Electrons are not emitted if the light frequency is below a certain threshold, regardless of intensity

Question 4

A photon has energy $$E = h f. $$What is its momentum $$p$$?

Accepted Answer

$$p = \frac{h f}{c}$$

Question 5

In the Compton effect, X-rays are scattered from electrons and the wavelength of the scattered X-rays increases. Which equation describes the change in wavelength?

Accepted Answer

$$\Delta \lambda = \lambda' - \lambda = \frac{h}{m_e c} (1 - \cos 	heta)$$

Question 6

Which of the following is NOT a possible photon interaction with matter?

Accepted Answer

Photon absorption resulting in neutron emission

Question 7

In pair production, which conservation laws must be satisfied?

Accepted Answer

Energy, electric charge, and momentum

Question 8

Which principle states that both the wave and particle aspects of light are fundamental to its nature?

Accepted Answer

The principle of complementarity

Question 9

According to de Broglie’s hypothesis, what is the wavelength $$\lambda$$ associated with a particle of momentum $$p$$?

Accepted Answer

$$\lambda = \frac{h}{p}$$

Question 10

Why are electrons suitable for use in electron microscopes for imaging very small objects?

Accepted Answer

Electrons have very short wavelengths at high energies, allowing resolution of small objects

Question 11

Rutherford’s gold foil experiment led to which conclusion about atomic structure?

Accepted Answer

Atoms have a tiny, dense, positively charged nucleus

Question 12

The Balmer series describes the visible spectral lines of hydrogen. Which equation gives the wavelengths of these lines?

Accepted Answer

$$\frac{1}{\lambda} = R \left( \frac{1}{2^2$} - \frac{1}{n^2$} \right)$$, where $$n \u003e 2$$

Question 13

According to Bohr’s model, what is the quantization condition for the angular momentum $$L of an $$electron in orbit?

Accepted Answer

$$L = n \frac{h}{2\pi}$$,\quad n = 1, 2, 3, ...$

Question 14

Which statement best explains why electrons in Bohr’s model do not radiate energy while in stable orbits?

Accepted Answer

Electrons occupy quantized orbits where their waveforms form standing waves, preventing energy loss

Question 15

A scanning tunneling microscope (STM) produces images by:

Accepted Answer

Maintaining a constant current as the probe moves up and down over the surface

Question 16

Which of the following best describes the correspondence principle in quantum theory?

Accepted Answer

Quantum predictions must agree with classical physics when quantum effects are negligible

Question 17

A metal surface is illuminated with light of frequency $$f$$ above the threshold frequency. If the intensity of the light is doubled, what happens to the number and kinetic energy of emitted electrons?

Accepted Answer

The number of emitted electrons doubles, but their kinetic energy remains unchanged

Question 18

Which real-world application relies directly on the photoelectric effect?

Accepted Answer

Electric eye detectors used in automatic doors

Question 19

Which model of the atom was disproved by Rutherford’s gold foil experiment?

Accepted Answer

The plum-pudding model

Question 20

Which statement about atomic spectra is correct?

Accepted Answer

Atoms emit light only at specific frequencies, resulting in line spectra

Chpt 27

Study Guide - Practice Questions

Study Guide - Flashcards