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MDCAT Prep · Physics · Quick Reference
Lesson 13 — Waves & Electricity Cheat Sheet
In one line: Sound needs a medium and light doesn't; Snell's law bends light between media; Ohm's law and Kirchhoff's laws run every circuit.
Key Ideas
1Wave equation. v = fλ, T = 1/f.
2Sound vs light. Sound = longitudinal, needs medium. Light = transverse, no medium.
3Snell's law. n1 sinθ1 = n2 sinθ2.
4Ohm's & power laws. V = IR. P = VI = I²R = V²/R.
5Kirchhoff's laws. Junction: ΣIin = ΣIout. Loop: ΣV = 0 around any closed loop.
Circuit Formulas
Series: R_total = R1 + R2 + ...
Parallel: 1/R = 1/R1 + 1/R2 + ...
Parallel resistance vs smallest resistor
Always smaller
Series resistance vs largest resistor
Always larger