Waves and Simple Harmonic motion

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Across
  1. 3. combination of waves
  2. 4. needs a medium to travel
  3. 5. distance to crest or trough
  4. 9. slope of F vs x for spring
  5. 11. interference type enhancing waves
  6. 13. interference canceling waves
  7. 15. simple harmonic motion
  8. 16. trough of sound wave
  9. 17. top of the wave
  10. 19. time for a wave cycle
  11. 20. particles travel forward horizontally
Down
  1. 1. distance for one cycle
  2. 2. determines wave speed
  3. 6. particles travel up and down
  4. 7. spring force is this type
  5. 8. crest of sound wave
  6. 10. type of SHM
  7. 12. lowest point of a wave
  8. 14. wave which doesn't need medium
  9. 18. inverse of period