Across
- 3. diminution in the density of something
- 4. to vibrate
- 8. a hollow between two wave crests in the sea
- 9. allowing light to pass through
- 10. not transparent
- 13. sounds caused by the reflection of sound waves from a surface
- 14. one thing absorbs or is absorbed by another
- 15. surface curved
- 16. automatic
- 18. curling foamy top of a wave
- 19. a space entirely devoid of matter
Down
- 1. extending across something
- 2. throwing back by a body or surface of light, heat, or sound without absorbing it
- 5. change in direction of propagation of any wave
- 6. interrelation of electric currents
- 7. being compressed
- 11. a force acts on objects at a distance
- 12. triangular with refracting surfaces at an acute angle
- 17. measured from east to west