Waves crossword

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Across
  1. 6. A change in observed frequency when a source moves relative to an observer
  2. 9. Wavelength multiplied by frequency
  3. 10. Sound cannot travel through this
  4. 12. When a wave changes direction as it enters a different medium
  5. 14. Type of wave where vibrations are parallel to the direction of travel
  6. 15. The time taken for one complete wave to pass a point
  7. 17. The number of waves passing a point per second
  8. 18. Type of wave where vibrations are at right angles to the direction of travel
  9. 19. A repetitive back-and-forth motion
Down
  1. 1. A transverse electromagnetic wave
  2. 2. A region in a longitudinal wave where the particles are close together
  3. 3. A substance through which a wave travels
  4. 4. When a wave bends around obstacles or spreads through gaps
  5. 5. The unit of frequency
  6. 7. When a wave bounces off a surface
  7. 8. The maximum displacement from the rest position in a wave
  8. 11. A region in a longitudinal wave where the particles are spread out
  9. 13. A line connecting points of equal phase in a wave
  10. 16. The distance between two successive crests or troughs in a wave