• summary_type: application
• word_count: 170

Five essential graphs: (1) Photocurrent vs V: rises from zero at -$V_{0}$ to saturation; different intensities give same $V_{0}$ but different saturation. (2) $V_{0}$ vs f: straight line, slope h/e, key graph for JEE. (3) KE_max vs f: straight line, slope h. (4) Photocurrent vs intensity: linear. (5) $V_{0}$ vs λ: hyperbolic (not linear). Calculation strategy: always start with E = 1240/λ(nm) to get photon energy in eV. Then KE_max = E - φ gives the stopping potential directly in volts. For velocity: v = √(2KE/m). For de Broglie wavelength of photoelectrons: λ = 12.27/√(KE in eV) Å. Common traps: confusing intensity effects (affects count) with frequency effects (affects energy), and assuming KE ratio equals frequency ratio (it doesn't, because of the work function subtraction). Always check whether the photon energy exceeds the work function before proceeding.