Laser beam used to measure dirt content of water, June, pp. 112, 1973. Laser interferometer, how to make a simple, Feb., pp. 106, 1972. Lasers, how to make: helium-neon type, Sep., pp. 227, 1964. Lasers, how to make: helium-neon type, … המשך לקרוא Scientific American “Amateur Science” Articles