Doppler Effect: Source Approaching Stationary Observer

Steps:

• Use Doppler formula for source moving toward stationary observer: f' = f × (v / (v - v_s)), where f = 2000 Hz, v = 340 m/s, v_s = 30 m/s.
• Compute denominator: v - v_s = 340 - 30 = 310 m/s.
• Compute ratio: 340 / 310 ≈ 1.09677.
• Multiply: 2000 × 1.09677 ≈ 2193.5 Hz, which rounds to 2190 Hz.

Why D is correct:

• The formula f' = f × (v / (v - v_s)) accounts for compressed wavefronts as the source approaches, increasing observed frequency per Doppler principle.

Why the others are wrong:

• A: Applies to source receding (f' = f × (v / (v + v_s))), decreasing frequency.
• B: Assumes no relative motion, so no frequency shift.
• C: Results from approximate calculation error, like using 330 m/s for v instead of 340 m/s.

Final answer: D