1 Reading the notation

Modern physics deals in very small numbers and specific constants. Each symbol below appears on this page.

8 terms

Cover the right column and check you can say what each one means.

h (Planck constant): 6.63 × 10⁻³⁴ J s. Links a photon’s energy to its frequency: E = hf.
f and λ: Frequency (Hz) and wavelength (m) of the photon. Related by c = fλ, so E = hf = hc/λ.
φ (phi: work function): The minimum energy needed to free an electron from a metal’s surface. A property of the METAL, not of the light.
E_k(max): The maximum kinetic energy of an emitted photoelectron: E_k(max) = hf − φ.
eV (electronvolt): An energy unit: the energy gained by one electron accelerated through 1 volt. 1 eV = 1.602 × 10⁻¹⁹ J. Energy levels are usually tabulated in eV, convert to joules before using E = hf.
Δm (mass defect): The difference between a nucleus’s mass and the sum of its separate nucleons. Its energy equivalent is the binding energy, E = Δmc².
t_½ (half-life): The time for half the radioactive nuclei in a sample to decay.
Superscript before an element (²³⁵U): The mass number, protons + neutrons, naming a specific isotope. Same convention as ¹³C in chemistry.

✓

Multiply by 1.602 × 10⁻¹⁹. Forgetting this is the most common error in photoelectric calculations. The answer comes out about 10¹⁹ times too big.

Practice for this standard covers the whole topic — flashcards and quiz.