Quantum Physics: Black Body Radiation, Photoelectric & Compton Effects, and Wave-Particle Duality: 25 flashcards
All 25 flashcards from this kit, free and with no sign-up.
1. What is black body radiation?
Show the answer
The spectrum of electromagnetic radiation emitted by a perfect absorber and emitter (a black body), which depends only on its temperature.
2. What was the ultraviolet catastrophe?
Show the answer
The classical Rayleigh–Jeans law predicted infinite energy emission at short wavelengths, which contradicted experiments.
3. State Planck's quantum hypothesis.
Show the answer
Energy is emitted or absorbed in discrete packets called quanta, with energy $E = h\nu$.
4. What is the value of Planck's constant $h$?
Show the answer
$h = 6.626 \times 10^{-34}$ J·s
5. Define the photoelectric effect.
Show the answer
The emission of electrons from a metal surface when light of frequency above a threshold falls on it.
6. What is threshold frequency in the photoelectric effect?
Show the answer
The minimum frequency $\nu_0 = \phi/h$ below which no electrons are emitted, regardless of light intensity.
7. Write Einstein's photoelectric equation.
Show the answer
$K_{max} = h\nu - \phi$, where $\phi$ is the work function.
8. What is the work function $\phi$?
Show the answer
The minimum energy required to remove an electron from the surface of a metal.
9. What is the Compton effect?
Show the answer
The increase in wavelength of X-rays when scattered by free electrons.
10. Write the Compton shift formula.
Show the answer
$\Delta\lambda = \frac{h}{m_e c}(1 - \cos\theta)$
11. What is the Compton wavelength of the electron?
Show the answer
$h/m_e c = 2.426$ pm
12. At what angle is the Compton shift maximum, and what is its value?
Show the answer
At $\theta = 180^\circ$, the shift is maximum and equals $2h/m_e c = 4.852$ pm.
13. What did the Davisson–Germer experiment demonstrate?
Show the answer
Electrons diffract like waves, confirming de Broglie's matter wave hypothesis.
14. State Heisenberg's uncertainty principle for position and momentum.
Show the answer
$\Delta x \cdot \Delta p \geq \frac{h}{4\pi}$
15. What is the physical meaning of the wave function $\psi$?
Show the answer
$|\psi|^2$ gives the probability density of finding the particle at a given position and time.
16. List the conditions a valid wave function must satisfy.
Show the answer
It must be single-valued, continuous, finite, and normalizable.
17. Write the normalization condition for a wave function.
Show the answer
$\int_{-\infty}^{\infty} |\psi|^2 dx = 1$
18. Calculate the energy of a photon with frequency $5 \times 10^{14}$ Hz.
Show the answer
$E = h\nu = (6.626 \times 10^{-34})(5 \times 10^{14}) = 3.313 \times 10^{-19}$ J
19. If work function is 2.0 eV and photon energy is 3.5 eV, find $K_{max}$.
Show the answer
$K_{max} = 3.5 - 2.0 = 1.5$ eV
20. Find the Compton shift for scattering at $90^\circ$.
Show the answer
$\Delta\lambda = 2.426$ pm $\times (1 - \cos 90^\circ) = 2.426$ pm
21. Find the minimum uncertainty in momentum if an electron is confined to $1 \times 10^{-10}$ m.
Show the answer
$\Delta p \geq \frac{h}{4\pi \Delta x} = 5.27 \times 10^{-25}$ kg m/s
22. What is the momentum of a photon?
Show the answer
$p = h/\lambda$
23. What is the de Broglie wavelength of a particle?
Show the answer
$\lambda = h/p$
24. Why does classical wave theory fail to explain the photoelectric effect?
Show the answer
It predicts that brighter light gives more energetic electrons and any frequency works, but experiments show a threshold frequency and intensity-independent kinetic energy.
25. What is the energy–time uncertainty relation?
Show the answer
$\Delta E \cdot \Delta t \geq \frac{h}{4\pi}$
Your notes can be a kit like these
Every kit here was made from real study material. Point Veda at a chapter, a PDF, a photo or a link and get notes, flashcards, practice MCQs, games and a scored test — free, in 42 languages.
- Chapter notes
- Flashcards
- Practice MCQs
- Scored tests
- Exam prep
Get Veda free See what students get
Free to start · No ads · Works in 42 languages