Fyzika mikrosveta a atómová fyzika
What you must know
This domain spans the structure of the atom (nucleus of protons and neutrons, electrons), the photon model E = hf, the photoelectric effect, atomic spectra and energy levels (E = hf for emitted/absorbed photons), and nuclear physics: alpha, beta and gamma decay, the mass–energy relation E = mc², and half-life. Know the notation for nuclides (A = mass number, Z = proton number) and that beta-minus decay converts a neutron into a proton, increasing Z by one.
Traps
- Mixing up atomic number Z (protons) with mass number A (protons + neutrons).
- Forgetting that photon energy depends on frequency, not intensity.
- In beta decay, forgetting the atomic number changes while mass number stays the same.
- Confusing half-life with mean lifetime.
- Using E = hf with wavelength instead of frequency (use f = c/λ).
Worked example
A sample has a half-life of 10 days. After 30 days, how much remains? 30/10 = 3 half-lives, so the fraction remaining is (1/2)³ = 1/8, i.e. 12.5% of the original. If the initial mass were 80 g, 10 g would remain - a standard calculation.
Rule of thumb: in every nuclear equation, the sum of mass numbers A and the sum of atomic numbers Z must be equal on both sides. Balance these first, then identify the emitted particle.