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The ratio of half-life times of two elements \(A\) and \(B\) is \(T_{A} / T_{B} .\) The ratio of respective decay constant \(\frac{\lambda_{A}}{\lambda_{B}}\) is (a) \(T_{B} / T_{A}\) (b) \(T_{A} / T_{B}\) (c) \(\frac{T_{A}+T_{B}}{T_{A}}\) (d) \(\frac{T_{A}-T_{B}}{T_{A}}\)

Short Answer

Expert verified
The ratio of decay constants \( \frac{\lambda_A}{\lambda_B} \) is \( \frac{T_B}{T_A} \), option (a).

Step by step solution

01

Understanding the Relationship Between Half-life and Decay Constant

The half-life of a radioactive element is related to its decay constant by the formula: \( T = \frac{0.693}{\lambda} \). Here, \( T \) is the half-life and \( \lambda \) is the decay constant of the element.For elements A and B, the formulas are:\[ T_A = \frac{0.693}{\lambda_A} \]\[ T_B = \frac{0.693}{\lambda_B} \]
02

Finding the Decay Constant Ratio

Given the half-life ratio \( \frac{T_A}{T_B} \), we need to express this in terms of decay constants. Substituting the half-life expressions, we have:\[ \frac{T_A}{T_B} = \frac{\frac{0.693}{\lambda_A}}{\frac{0.693}{\lambda_B}} \]This simplifies to:\[ \frac{T_A}{T_B} = \frac{\lambda_B}{\lambda_A} \]
03

Finding the Inverse For the Ratio of decay constants

From the previous step, we have \( \frac{\lambda_B}{\lambda_A} = \frac{T_A}{T_B} \). Therefore, the inverse will be:\[ \frac{\lambda_A}{\lambda_B} = \frac{T_B}{T_A} \]
04

Conclusion and Answer Selection

Looking at the given options, the decayed constant ratio \( \frac{\lambda_A}{\lambda_B} = \frac{T_B}{T_A} \) matches option (a). Therefore, the correct answer is option (a) \( \frac{T_B}{T_A} \).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Half-Life
Half-life is a term used to describe the time it takes for half of a given quantity of a radioactive substance to decay. This is a crucial concept in understanding radioactive decay processes.
In mathematical terms, if you start with 100 grams of a radioactive element, after one half-life, you'll be left with 50 grams. After another half-life, just 25 grams will remain, and so on.
The process is exponential, meaning the rate of decay slows down as time passes. This happens because there are fewer atoms left to decay as time goes on.

Importance of Half-life

- Half-life helps in predicting how long a substance will remain hazardous, such as in nuclear waste.
- It is useful in radiometric dating, helping scientists figure out the age of ancient objects by measuring isotopes.
Additionally, the half-life of a substance is mathematically expressed as:\[ T = \frac{0.693}{\lambda} \]where:- \(T\) is the half-life of the radioactive element.- \(\lambda\) is the decay constant, a measure of the rate at which the element decays.
Decay Constant
The decay constant is a measure that indicates the probability per unit time that a single atom will decay. In the realm of radioactive decay, it's a vital parameter that defines the decay behavior of a radioactive isotope.
It acts like a speed control knob. A higher decay constant means the substance decays more quickly, whereas a smaller decay constant means a slower decay rate.

Decay Constant and Its Connection to Half-life

The relationship between decay constant and half-life is inversely related, as shown in the expression:\[ T = \frac{0.693}{\lambda} \]This formula indicates that if the decay constant increases, the half-life decreases, meaning the substance will decay faster. Conversely, a smaller decay constant results in a longer half-life.
For example, if element A has a higher decay constant than element B, it implies that element A will reach its half-life faster than element B. Understanding this relationship allows scientists and engineers to predict the behavior of radioactive substances in different scenarios.
Radioactive Elements
Radioactive elements are substances that undergo spontaneous decay, releasing energy in the form of radiation. This decay happens because their atomic nuclei are unstable. The energy emitted during this process can take several forms, such as alpha particles, beta particles, or gamma rays.

Properties and Uses of Radioactive Elements

Some properties of radioactive elements include their ability to ionize matter, causing chemical reactions or damage in cells, and their characteristic half-lives that differ vastly from one element to another.
These elements are harnessed in various applications like:
  • Medical imaging and cancer treatment.
  • Power generation in nuclear reactors.
  • Carbon dating for archeological time scale studies.
Each radioactive element has its own unique decay path and rate, strongly influenced by its decay constant. By understanding the unique characteristics of each element, we can both harness their energy for constructive purposes, as well as implement protective measures against their potential hazards.

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Most popular questions from this chapter

Four vessels \(A, B, C\) and \(D\) contain respectively 20 g-atom \(\left(T_{1 / 2}=5 \mathrm{hr}\right), 2 \mathrm{~g}\) -atom \(\left(T_{1 / 2}=1 \mathrm{hr}\right), 5 \mathrm{~g}\) -atom \(\left(T_{1 / 2}=2 \mathrm{hr}\right)\) and \(10 \mathrm{~g}\) -atom \(\left(T_{1 / 2}=3 \mathrm{hr}\right)\) of different radio nucleides in the beginning, the maximum activity would be exhibited by the vessel, is (a) \(A\) (b) \(B\) (c) \(C\) (d) \(D\)

\(\mathrm{U}^{238}\) decays to \({ }_{90} \mathrm{Th}^{234}\) with half-life \(4.5 \times 10^{9}\) year. The resulting \({ }_{90} \mathrm{Th}^{234}\) is in excited state and hence, emits further a gamma ray to come to the ground state, with halflife of \(10^{-8} \mathrm{~s}\). A sample of \({ }_{92} \mathrm{U}^{238}\) emits 20 gamma rays per second. In what time, the emission rate will drop to 5 gamma rays per second? (a) \(2 \times 10^{-8} \mathrm{~s}\) (b) \(0.25 \times 10^{-8} \mathrm{~s}\) (c) \(9 \times 10^{9}\) year (d) \(1.125 \times 10^{9}\) year

There are three lumps of a given radioactive substance. Their activity is in the ratio of \(1: 2: 3\) now. What will be the ratio of their activities at any further date? (a) \(1: 2: 3\) (b) \(2: 1: 3\) (c) \(3: 2: 1\) (d) \(2: 3: 1\)

Which of the following statements is true regarding Bohr model of hydrogen atom? (I) Orbiting speed of electrons decreases as it falls to discrete orbits away from the nucleus. (II) Radii of allowed orbits of electrons are proportional to the principal quantum number. (III) Frequency with which electrons orbit around the nucleus in discrete orbits is inversely proportional to the principal quantum number. (IV) Binding force with which the electron is bound to the nucleus increases as it shifts to outer orbits. Select the correct answer using the codes given below (a) I and III (b) II and IV (c) I, II and III (d) II, III and IV

The wavelength involved in the spectrum of deuterium \(\left(D_{1}^{2}\right)\) are slightly different from that of hydrogen spectrum, because (a) size of the two nuclei are different (b) masses of the two nuclei are different (c) nuclear forces are different in the two cases (d) attraction between the electron and the nucleus is different in two cases

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