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Across 4. _________ are given off when fast-moving electrons lose energy very quickly 5. The rate at which something occurs over a particular period of time or in a given sample 6. The SI unit for frequency 7. Detects positions of aircraft or ships 9. Sounds above the range of human hearing are ultrasonic, or ___________ 11. The maximum distance a point moves from its rest position when a wave passes. 12. Light-emmiting-diode 15. The only radiation visiable to the eye 17. For long distance transmittion, telephone networks often use __________ 19. Very hot objects, emit some of their radiation beyond the end on the visiable spectrum. This radiation is called ______________ 20. Hard surfaces such as walls reflect sound waves

Down 1. This is the distance between any point on a wave and equivalent point on the next. 2. 300000 km/s.what is this speed? 3. _________ have the shortest wavelength of all radio waves 8. ______ come from radioactive materials, they are produced when ustable atoms break up 10. The name for wave movements, which move up and down and side to side. 13. The waves bend round the sides of an obstacle, or spread out as they pass through a gap. 14. The waves are refected from the surface at the same angle as they strike it 16. When waves move slow, they change direction. 18. the quality of a sound governed by the rate of vibrations producing it; the degree of highness or lowness of a tone.