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Across 2. Radiation given off by mercury lamps 5. Measure of the brightness of the light reflected from a surface 9. Gas contained in some types of filament lamps 11. Provides the starting voltage and current control 13. Type of starter used in flourescent lamp circuits 14. Type of discharge lamp 16. Lamp output compared to energy input 18. The ability of the lamp to show colours faithfully 20. Name given to the outer glass vessel of lamp 21. Measurement of power 22. Name of filament in discharge lamps 23. Device which splits light into seven colours

Down 1. Takes into account deterioration of reflecting surface and light output 3. Filaments are made from this metal 4. Light is this type of radiation 6. Type of vapour contained in flourescent lamps 7. Light consisting entirely of one wavelength 8. Device used in discharge lamp circuits to improve power factor 10. Flow of light radiated fron a single source 12. These types of lamps do not rely on the heating of a filament to produce light 15. Type of square law 17. Lamp will not restrike if mains fails until this has reduced through cooling 19. Type of lamp often used for street lighting