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Across 3. Particles of a medium vibrate perpendicularly to the direction of the motion of the wave. 4. Work done devided by the time taken to do the work. 8. The perpendicular distance from the axis of rotation to the point where the force is exerted. 11. The bending around obstacles. 15. The speed of sound depends on ... 16. Combination of transverse and longitudinal water waves. 18. Particles of a medium travel parallel to the direction of the wave. 19. Source of all waves is something that ... 20. The net force of an object moving in a circle towards the center of the circle. 21. The change in angular velocity divided by the time required to make the change.

Down 1. The change in direction or bending of light at the boundary between two media. 2. Light rays converge at a point (can be projected onto a screen). 5. The distance from one crest to the other crest. 6. This wave needs a medium through which they can travel. 7. The force of attraction between two objects must be proportional to the object's masses. 9. The incident angle that causes the refracted ray to lie right along the boundary of the substance is unique to the substance. 10. Light rays do not converge at a point (can't be projected on a screen). 12. Number of oscillatims in pressure each second heard as pitch. 13. Determines speed of light in the medium. 14. Which of Kepler's law states that the planets move in elliptical orbits, with the sun at one focus? 17. What mirror reflects light from its inner curved surface.