0.22 m Image is now virtual, Natural sources. inverted and magnified. -20 D Radiation kills or alters cells. (a) i Virtual Properties of Radiation ii Magnified (p16 – 17) Alpha particles ionise air, iii Upright allowing electrons to pass (a) Helium nucleus through ions, completing a i Real Fast electron circuit. ii Diminished Electromagnetic wave Smoke particles are not iii Inverted ionised so stop the circuit Ionisation is the process by from completing. (a) Short sighted people can which an atom loses (or An alarm sounds. see nearby objects clearly gains) an electron. but distant objects appear Tracer is injected in to blurry. (a) Alpha particles are patient. Gamma rays leave Long sighted people can positively charged, so the body and are detected see distant objects clearly attract electrons away by a gamma camera. but nearby objects from nuclei. The circulatory system can appear blurry. Beta particles are then be seen. negatively charged, so (a) Short sight is corrected repel electrons away Gamma rays can be with a concave lens. from nuclei. directed at cancer cells to Gamma rays are kill them. absorbed by electrons Gamma source is rotated giving them the energy to prevent healthy tissue required to leave being overexposed. atoms. Long sight is corrected with G-M tube – radiation detected a convex lens. Alpha can’t pass through by a circuit being completed by any materials. ionised gas. Beta can pass through air Film badge – radiation and paper. detected by darkening of film. Gamma can pass through Scintillation counter – air, paper and aluminium. radiation detected by a small pulse of light. Use tongs, point source away from people, wear Objective lens has a focal lead-lined clothing, keep in Activity (p18 – 19) length less than the length a lead lined container. of the light-tight tube. (a) 12 Bq It creates an image that is Background radiation is 25 Bq real, inverted and radiation that is around us 100 000 diminished. all the time. 6 250 000 Eyepiece lens has a focal 750 s length bigger than the Radon gas, medical, 200 s distance to the image from buildings, food, cosmic the objective lens. rays.
0.22 m -20 D (a) i Virtual ii Magnified iii Upright i Real ii Diminished iii Inverted (a) Short sighted people can see nearby objects clearly but distant objects appear blurry. Long sighted people can see distant objects clearly but nearby objects appear blurry. (a) Short sight is corrected with a concave lens. Long sight is corrected with a convex lens. Objective lens has a focal length less than the length of the light-tight tube. It creates an image that is real, inverted and diminished. Eyepiece lens has a focal length bigger than the distance to the image from the objective lens. Image is now virtual, inverted and magnified. Properties of Radiation (p16 – 17) (a) Helium nucleus Fast electron Electromagnetic wave Ionisation is the process by which an atom loses (or gains) an electron. (a) Alpha particles are positively charged, so attract electrons away from nuclei. Beta particles are negatively charged, so repel electrons away from nuclei. Gamma rays are absorbed by electrons giving them the energy required to leave atoms. Alpha can’t pass through any materials. Beta can pass through air and paper. Gamma can pass through air, paper and aluminium. Use tongs, point source away from people, wear lead-lined clothing, keep in a lead lined container. Background radiation is radiation that is around us all the time. Radon gas, medical, buildings, food, cosmic rays. Natural sources. Radiation kills or alters cells. Alpha particles ionise air, allowing electrons to pass through ions, completing a circuit. Smoke particles are not ionised so stop the circuit from completing. An alarm sounds. Tracer is injected in to patient. Gamma rays leave the body and are detected by a gamma camera. The circulatory system can then be seen. Gamma rays can be directed at cancer cells to kill them. Gamma source is rotated to prevent healthy tissue being overexposed. G-M tube – radiation detected by a circuit being completed by ionised gas. Film badge – radiation detected by darkening of film. Scintillation counter – radiation detected by a small pulse of light. Activity (p18 – 19) (a) 12 Bq 25 Bq 100 000 6 250 000 750 s 200 s