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Across 3. Spectrum of coloured waves that allow us to see 5. Telescope we look through using our eyes 9. Putting telescopes in space or high up mountains reduces distortion due to the gases in this 11. Nuclear radiation rays travelling at speed of light that can penetrate almost anything 13. Old style signals used for communication, prone to interference 14. Electromagnetic waves with the longest wavelengths 15. Telescopes that use large dishes to gather forms of electromagnetic waves 17. Name given to the way radiation can cause atoms to become charged & cells to become mutated/cancerous 21. Tiny particles surrounding the centre of an atom 22. Nuclear radiation made up very fast electrons that need 3mm of aluminium to stop them 23. Rays used to produce images of bones and teeth 24. The average time it takes for half the unstable atoms/nuclei to decay 25. Element with the same number of protons but different number of neutrons in its nucleus 26. type of nuclear radiation that can be used to sterilise food & surgical instruments, plus kill cancer cells

Down 1. The speed all electromagnetic waves travel 2. Rays given off by the sun that cause us to tan and burn 4. Electromagnetic rays with the shortest wavelengths 6. Waves given off by all hot objects. Also used for remote controls 7. Nuclear radiation made up of slow moving helium nuclei that cannot penetrate paper 8. The name for radiation found naturally all around us 10. Type of waves used for TV & radio 12. The beginning of time and the universe 16. Type of waves used for cooking & mobile phone communications 18. The centre of an atom containing protons & neutrons 19. The name given to light changing towards the red end of the spectrum as galaxies are moving away from each other 20. Signals that can be passed through optical fibres used for broadband & cable TV