Evaluate the following statements:
S1: The Doppler Effect describes the change in frequency of a wave in relation to an observer who is moving relative to the wave source.
S2: Sound waves can travel through a vacuum.
S3: Ultrasonic waves are sound waves with frequencies higher than 20 kHz, commonly used in medical imaging.
1
S1 is true; S2 and S3 are false
2
All S1, S2, and S3 are true
3
S1 and S3 are true; S2 is false
4
S2 and S3 are true; S1 is false