📈 V0 vs ν — a straight line of slope h/e, the same for every metal

Measure the stopping potential V0 at several frequencies for one metal and the points fall on a straight line, V0 = (h/e)(ν − ν0). The slope is h/e for EVERY metal — the lines are parallel — and only the threshold ν0 shifts. Multiply the slope by e and you have measured Planck's constant.
For one metal, measure the stopping potential V0 at several frequencies — the points lie on a straight line.
V₀ = (h/e)(ν − ν₀) · slope h/e = 4.14×10⁻¹⁵ V·s
V₀ = — V · threshold ν₀ = — e14 Hz