| 单词 | 曝光表 |
| 释义 | 〔selenium〕A nonmetallic element, red in powder form, black in vitreous form, and metallic gray in crystalline form, resembling sulfur and obtained primarily as a byproduct of electrolytic copper refining. It is widely used in rectifiers, as a semiconductor, and in xerography. Its photovoltaic and photoconductive actions make it useful in photocells, photographic exposure meters, and solar cells. Atomic number 34; atomic weight 78.96; melting point (of gray selenium) 217°C; boiling point (gray) 684.9°C; specific gravity (gray) 4.79; (vitreous) 4.28; valence 2, 4, or 6. See table at element 硒：一种非金属元素，粉末状时呈红色，玻璃状时呈黑色，结晶状时呈金属般的灰色，与硫类似，通常作为副产品在电解法冶炼铜时获得。广泛地用于整流器（如半导体）和静电复印术中。其光电压的和光电导的效应使它可在光电池、照相曝光表和太阳能电池中发挥作用。原子序数34；原子量78.96；（灰色硒的）熔点217°C；沸点（灰色硒的）684.9°C；（灰色硒的）比重4.79；（玻璃状的硒）比重4.28；化合价2,4或6 参见 element〔sensitometer〕A device used for measuring the sensitivity of photographic film to light.曝光表：用于测量摄影用的胶片对光的感光度的设备 |
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