Q: Wien's law relates the temperature of a blackbody to the wavelength at which it emits most strongly. If a star emits its peak radiation at $$500 \text{ nm}$$, what is its approximate surface temperature?

$$T = \frac{2.898 \times 10$$^{-3}$$ \text{ m} \cdot \text{K}}{500 \times 10$$^{-9}$$ \text{ m}} \approx 5800 \text{ K}$$

Q: In Bohr's model of the hydrogen atom, what happens when an electron transitions from a higher energy orbit to a lower energy orbit?

A photon is emitted with energy $$hf = E_{\text{high}} - E_{\text{low}}$$

Q: A metal has a work function $$\phi = 2.0 \text{ eV}. $$What is the minimum frequency of light required to emit electrons from this metal?

$$f_c = \frac{2.0 \text{ eV}}{4.136 \times 10$$^{-15}$$ \text{ eV} \cdot \text{s}} \approx 4.83 \times 10$$^{14}$$ \text{ Hz}$$

Q: What is the unit of electric current, and how is it defined?

Ampere, defined as $$1 \text{ A} = 1 \text{ C/s}$$

Question 1

According to Planck's quantum hypothesis, what is the energy of a photon with frequency $$f$$?

Accepted Answer

$$E = hf$$

Question 2

Wien's law relates the temperature of a blackbody to the wavelength at which it emits most strongly. If a star emits its peak radiation at $$500 	ext{ nm}$$, what is its approximate surface temperature?

Accepted Answer

$$T = \frac{2.898 	imes 10$$^{-3}$$ 	ext{ m} \cdot 	ext{K}}{500 	imes 10$$^{-9}$$ 	ext{ m}} \approx 5800 	ext{ K}$$

Question 3

Which experiment provided evidence for the particle nature of light by showing that electrons are emitted from a metal only when the incident light exceeds a certain frequency?

Accepted Answer

Photoelectric effect

Question 4

In the photoelectric effect, what happens if the frequency of incident light is below the cut-off frequency for a given metal?

Accepted Answer

No electrons are emitted, regardless of light intensity

Question 5

The maximum kinetic energy of photoelectrons in the photoelectric effect is given by $$K_{	ext{max}} = hf - \phi. $$What does $$\phi$$ represent?

Accepted Answer

The work function of the metal

Question 6

A photon has a wavelength $$\lambda = 400 	ext{ nm}. $$What is its momentum?

Accepted Answer

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

Question 7

Which of the following best describes the difference between coherent and incoherent light, as seen in lasers?

Accepted Answer

Coherent light has photons with the same frequency and phase; incoherent light has photons with different frequencies and phases

Question 8

According to the Heisenberg uncertainty principle, what is the minimum product of the uncertainties in position and momentum?

Accepted Answer

$$\Delta x \Delta p \geq \frac{\hbar}{2}$$

Question 9

In the Compton effect, what is observed when X-rays scatter off electrons?

Accepted Answer

The wavelength of the X-rays increases, confirming the particle nature of light

Question 10

De Broglie's hypothesis states that particles have a wavelength given by $$\lambda = \frac{h}{p}. $$What does $$p$$ represent?

Accepted Answer

The momentum of the particle

Question 11

A laser emits light at a wavelength of $$405 	ext{ nm} ($$Blu-Ray). Compared to a CD laser ($$780 	ext{ nm}$$), what is the main advantage of the Blu-Ray laser?

Accepted Answer

It allows for higher data storage density due to shorter wavelength

Question 12

In Bohr's model of the hydrogen atom, what happens when an electron transitions from a higher energy orbit to a lower energy orbit?

Accepted Answer

A photon is emitted with energy $$hf = E_{	ext{high}} - E_{	ext{low}}$$

Question 13

Which phenomenon demonstrates the wave-particle duality of electrons?

Accepted Answer

Double-slit interference experiment

Question 14

If the intensity of light in a photoelectric experiment is increased, but the frequency remains below the cut-off frequency, what is observed?

Accepted Answer

No electrons are emitted

Question 15

Which equation gives the cut-off frequency for the photoelectric effect?

Accepted Answer

$$f_c = \frac{\phi}{h}$$

Question 16

A metal has a work function $$\phi = 2.0 	ext{ eV}. $$What is the minimum frequency of light required to emit electrons from this metal?

Accepted Answer

$$f_c = \frac{2.0 	ext{ eV}}{4.136 	imes 10$$^{-15}$$ 	ext{ eV} \cdot 	ext{s}} \approx 4.83 	imes 10$$^{14}$$ 	ext{ Hz}$$

Question 17

Which of the following is NOT explained by classical physics, but is explained by quantum theory?

Accepted Answer

Photoelectric effect

Question 18

What is the unit of electric current, and how is it defined?

Accepted Answer

Ampere, defined as $$1 	ext{ A} = 1 	ext{ C/s}$$

Question 19

Which statement best describes the statistical interpretation of the wave function in quantum mechanics?

Accepted Answer

The square of the wave function gives the probability density of finding a particle at a given position

Quantum Physics and the Photoelectric Effect: Study Guide

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