AST201H1 Lecture 7: Lecture#7 Jan.27th
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AST201H1 Full Course Notes
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*the sun"s diameter is about 100 times earth"s diameter. *the sun is about 8 light minutes from earth. *the sun is about 4. 6 billion years old. Until 1925, people assumed the sun was made of similar material to the earth. In 1925, cecelia payne showed that, in fact, the sun was made mostly of hydrogen, a little helium, and tiny amounts of other elements. The sun is made of 70% hydrogen, 28% helium, and 2% other elements. Emission: a light bulb emits visible light; the energy of the light comes from electrical potential energy supplied to the light bulb. Absorption: when you place your hand near an incandescent light bulb, your hand absorbs some of the light, and this absorbed energy warms your hand. Transmission: some forms of matter, such as glass or air, transmit light, which means allowing it to pass through.