Physics of a Compact Disk essays

Physics of a Compact Disk essays Compact discs are the most popular form of recorded musical entertainment. They have more memory than their vinyl predecessors as well as a smaller size. Compact discs are digitally recorded, unlike the analog-recorded tapes and LP records, so have a better sound quality. Because of the benefits of optically recorded compact discs, this form of musical technology has almost completely replaced vinyl records and cassette tapes. CDs are played optically by a compact disk player. Laser light beams read the binary codes encoded on the disk during recording, and the code is interpreted as sound or silence. The more binary numbers there are that are read as sound, the greater the intensity of the sound. The sound is transferred to the compact disc players sound system and the music is amplified through the speakers. Compact discs are digitally recorded using an optical recording system. Music, or sound, is recorded in analog form through a microphone placed near each instrument. The original sound signal is continuous and varies in pitch, or frequency, and volume. The microphone changes the air vibrations that correspond with analog sound waves into electronic signals. These signals are measured up to thousands of times per second and are changed to binary numbers which represent varying sounds. These binary numbers are digitally recorded and are sent as a stream of laser light pulses through a fiber to be read by a photodetector in the recording system. Each light pulse is read as a single bit of information. A binary 1 is recorded sound, and binary 0 is a pause or silence. The laser flashes encode digital information onto the light sensitive compact disc to record the digital information. When all of the necessary information is on the compact disc, it is placed in a chemical that s eals the digital information in the disc. Microscopic pits are left in th ...

What Are the Benefits of Recycling Metal

What Are the Benefits of Recycling Metal The United States recycles 150 million metric tons of scrap materials annually, including 85 million tons of iron and steel, 5.5 million tons of aluminum, 1.8 million tons of copper, 2 million tons of stainless steel, 1.2 million tons of lead and 420,000 tons of zinc, according to the Institute of Scrap Recycling Industries (ISRI). Other metals such as chrome, brass, bronze, magnesium, and tin are recycled as well. What Are the Benefits of Recycling All That Metal? By definition, mining metal ores and refining them into usable metals is unsustainable; the amount of metals present on earth is fixed when considering (at least when considering any useful geological time scale). However, metals are easily recycled and reused, providing renewed opportunities for their use without having to mine and refine more of it. Thus, issues associated with mining like can be avoided, like  acid mine drainage.  By recycling, we reduce the need to manage extensive and potential dangerous piles of mine tailings.   U.S. Exports Recycled Metal In 2008, the scrap recycling industry generated $86 billion and supported 85,000 jobs. The recycled materials that the industry processes into raw material feedstock every year are used for industrial manufacturing around the world. For example, 25% of the steel used in production car panels (doors, hood, etc.) is obtained from recycled materials. For copper, used in the home building industry for electric wires and plumbing pipes, that proportion surpasses 50%. Each year, the United States exports staggering amounts of scrap metals - called scrap commodities  -  contributing significantly to U.S. trade balances. For example, in 2012 the U.S. exported $3 billion worth of aluminum, $4 billion of copper, and $7.5 billion of iron and steel. Metal Recycling Saves Energy and Natural Resources Recycling scrap metal reduces the substantial amounts of  greenhouse gas emissions  produced during the various smelting and processing operations used when making metal from virgin ore. At the same time, the amount of energy used is also much smaller. Energy  savings using various recycled metals compared to virgin ore is up to: 92 percent for aluminum 90 percent for copper 56 percent for steel These savings are significant, especially when scaled up to large production capacities. Indeed, according to the U.S.Geological Survey, 60% of steel production comes directly from recycled iron and steel scrap. For copper, the proportion coming from recycled materials reaches 50%. Recycled copper is almost as valuable as new copper, making it a common target for scrap metal thieves. Metal recycling also conserves natural resources. Recycling one ton of steel conserves 2,500 pounds of iron ore, 1,400 pounds of coal and 120 pounds of limestone. Water is also used in great quantities in the manufacturing of many metals. According to an industry source, through recycling steel the amount of energy conserved would be enough to power 18 million homes for an entire year.  Recycling a ton of aluminum conserves up to 8 tons of bauxite ore and 14-megawatt hours of electricity.That figure does not even account for shipping the bauxite from where it is mined, generally in South America.  The total amount of energy saved in 2012 by making aluminum from recycled material added up to 76 million megawatt hours of electricity.​ Edited by Frederic Beaudry.