Soal Try Out Bahasa Inggris SBMPTN 2013 Kunci Jawaban III
Text AThe laws of radioactive decay hypothesize that once a living organism is dead, it does not interact with anything in its environment which would afffect the speed of decay of the unstable isotope of carbon 14. The C-14 is attached to organic molecules through photosynthesis in plants and becomes part of their molecular makeup. Animals eating those plants absorb Carbon-14 and the process of ingesting C-14 continues as long as the plants and animals are alive. Once the organism dies, the ratio of C-14 within its carcass starts to decrease.
The radiocarbon dating method is widely used to determine the age of remains of living organisms. With this method, the type of sample and the placement of it within a site are taken into account. The date assigned to the sample successfully collected will initially be given as a raw B.P. or “before present”. The “present” is set at the year 1950 on the Gregorian calender. The rate of decrease is ½ the quantity at death every 5.730 years, the half life of C-14. The date is usually callibrated with dendrochronology method to get a more absolute B.P.
Text BThe potassium-argon age method is another method widely used by archeologists and geologists to determine the time of origin of rocks. This is the most viable technique for dating old rocks because archeologists can use it to date rocks as much as 4 billion years old. Yet, it is not suitable to measure the age of rock 20,000 years before present. This method is widely used in archeology, particularly in East Africa.
This can be done by calculating the ratio of radioactive argon to radioactive potassium in the rock sample. Some of the radioactive isotope of Potassium, Potassium-40 (K-40) decays through a process of radiometric decay. Through beta decay, it results in calcium-40 and this occurs in almost 90% of cases. In molten rocks, it produces the gas Argon (known as Argon-40). The age of a certain rock can be determined through the calculation of the ratio and the decay rate of K-40. In this method, the rocks are heated to the melting point, and any Ar-40 contained is released into the atmosphere. When the rock recrystallizes, the decay of Potassium-40 continues at a constant rate but the argon-40 cannot escape and the gas is trapped in the rock. The amount of argon-40 is measured with a mass spectometer, while the potassium levels are measured using atomic absorpsion spectometry.
1. The two texts above mainly talk about ...
A.How radioactive materials are used to measure the age of organic materials.
B.The methods used to measure the age of rock and organis materials.
C.The use of radioactive potassium, argon and carbon
D.The laws of radioactive decay
E.The function of spectometer and spectometry
2. Which of the following is factual information explicitly supported by both texts?
A.The age of any materials can be accurately calculated using the two methods.
B.Sample collection is crucial in material age measurement.
C.The two methods measure the decay of radioactive.
D.Archeologists uses both methods for any investigation.
E.Similar heating process is used to generate radioactive materials measured.
3. From the two texts, we can conclude that, in both methods ...
A.The age measurement puts dendrochronology principle into account.
B.The use of spectometer is crucial.
C.Crystallized materials trap the radioactive gas.
D.Not any sample can be used for age measurement.
E.The amount of radioactive isotope of the sample tested should be high.
4. Based on the two texts, we can hypothesize that ...
A.The bigger sample is better than the smaller one.
B.The more gas is trapped, the older is the age of the organism.
C.The older materials have lesser radioactive content.
D.East Africa has been widely investigated by archeologists.
E.Extreme heat is required to calculate.
5. Which of the following statements is supported by both texts?
A.The potassium-argon method is more accurate
B.Only archeologists are familiar with the two methods.
C.The age of materials 20,000 years before present cannot be calculated.
D.The samples can be taken randomly.
E.The two methods are widely used in dating old materials.
1. B. The methods used to measure the age of rock and organis materials.
2. C. Thetwo methods measure the decay of radioactive.
3. D. Not any sample can be used for age measurement.
4. C. The older materials have lesser radioactive content.
5. E. The two methods are widely used in dating old materials.