Question
Lake Poway, in Poway, San Diego County, California, is a man-made freshwater lake -created with a little more intent than the Salton Sea. But, like the Salton Sea, the water in it came from the Colorado River. The ecosystem of Lake Poway is extensive, and consists of many biotic and abiotic factors. The lake serves as the drinking water supply for the city of Poway, and is treated very carefully by the city. For example, people are prohibited from contacting the water and pets are not allowed near the water. The water in the lake is very clean and clear as a result of these policies. Most of the fish in the lake were originally stocked by the California Department of Fish and Wildlife, and the stocking of fish in the lake continues today. The lake is popular with anglers, families, and hikers, and the facilities surrounding it constitute a large park that sees many visitors annually. The lake attracts many organisms (other than humans) that come for the water- and it attracts some organisms that come for potential meals. List the abiotic and biotic factors that make up Lake Poway's ecosystem, then answer the following questions: Abiotic Factors Biotic Factors What is the apex predator in the Lake Poway ecosystem? What organisms are the producers in the Lake Poway ecosystem? One of the organisms that "produces" energy in the Lake Poway ecosystem is a heterotroph. Can you figure out which one and how it produces the energy for the ecosystem? summarize the extent of the Lake Poway ecosystem. In other words, how far out does it extend? For example, Lake Poway's ecosystem doesn't extend to Los Angeles (or does it?), but it's influence is felt more locally. Predict what would happen to this ecosystem if humans ceased influencing it.
Explanation / Answer
NaI( Tl) scinitillation counter can just resolve Co-60 , 1170 and 1330 kev photo peaks
60 kev resolution over 1200 kev i.e 5 %
in case of 900 and 940 kev gama rays , the resolution required is
40/920 *100 = 4.3%,
the resolution required is higher than the scintillation counter has and hence the two gamarays cannot be fully resolved.
with scinitillation counter the countign efficiency is better , the detector size is larger and the gama rays are better abosrobed but the energy resolution is poorer as the signal strenth per unit energy absorbed is low.
with germanium counter the signal strenght is very high and gives much better energy resolution, however the detector size is very small and the counting efficiency is low, we need to count longer time for getting good statistics and use a multichannel analyser.
