Misconceptions — Waves & SHM — Notes | NoteTube

#	Misconception	Why It's Wrong	Correct Concept
1	"KE = PE at half the amplitude"	Equating KE and PE gives $x^{2}$ = $A^{2}$ /2, so x = A/√2 ≈ 0.707A	KE = PE at x = A/√2, not A/2
2	"Sound cannot travel in solids"	Sound requires a medium; solids provide the strongest elastic medium	Sound travels fastest in solids: v_solid > v_liquid > v_gas
3	"The spring period changes in space"	T = 2π√(m/k) has no g term	Spring-mass system works identically in zero gravity
4	"Nodes in a standing wave move slowly"	Nodes are permanently stationary — zero displacement always	Nodes are fixed points of zero displacement, not slow-moving
5	"First overtone = 2nd harmonic for all pipes"	Closed pipes skip even harmonics; 1st overtone = 3rd harmonic	Open/string: 1st overtone = 2nd harmonic; Closed: 1st overtone = 3rd harmonic
6	"Doppler effect changes actual frequency"	The source emits the same frequency; only apparent frequency changes	f' is what the observer perceives; the source frequency f is unchanged
7	"Louder sound means higher frequency"	Loudness ↔ intensity ↔ amplitu $de^{2}$ ; frequency ↔ pitch	Amplitude determines loudness; frequency determines pitch — independent
8	"A pendulum oscillates faster in a lift going down"	g_eff = g − a < g → T = 2π√(L/g_eff) increases → slower	Pendulum slows down in downward-accelerating lift
9	"Beat frequency = f_{1} + f_{2}"	Beats arise from the difference, not the sum	f_beat =
10	"Wave speed depends on amplitude"	v = fλ = √(T/μ) for strings; amplitude does not appear	Wave speed depends on medium properties, not amplitude