Doppler — Observer Moving

Observer moving, source stationary: apparent frequency changes.

Observer moving TOWARD source: encounters more waves per second ⇒ f' > f.

Observer moving AWAY from source: fewer waves per second ⇒ f' < f.

Formula: f' = f × (v ± v_o)/v. Plus when observer approaches.

v_o = observer speed; v = wave speed.

Same overall direction of shift as moving source, but DIFFERENT formula.

Magnitude depends on RATIO v_o/v.

Combined source + observer motion uses both numerator AND denominator changes.