A7. A sound wave.
A8. A source, medium, and detector (receiver).
A9. A sequence of events, such as the positive and negative alternation of electrical current.
A10. The space occupied by one cycle of a radio wave at any given instant.
A11. The law of reflection states: The angle of incidence is equal to the angle of reflection.
A12. When the incident wave is nearly parallel with the surface.
A13. When the incident wave is perpendicular to the surface. Also a dull (or black) surface reflects very
little regardless of the angle.
A14. The density of the two mediums, and the velocity of the waves.
A15. The Doppler effect.
A17. No. The average human ear cannot hear all sounds in the infrasonic and ultrasonic regions.
A18. An amplifier.
A19. A source, medium, and detector (receiver).
A20. Noise and tones.
A21. Pitch, intensity, and quality.
A22. 20 Hz to 20 kHz.
A23. The amount of energy transmitted from a source.
A25. Velocity increases as density decreases and temperature increases.
A31. Mechanical, electrical, and chemical.
A32. A photon.
A33. Angstrom unit.
A34. Red, green and blue.