JEE Mains · Physics · STD 11 - Units,dimensions and measurement
- JEE Mains 2019
- Hard
- MCQ
The force of interaction between two atoms is given by \(F\, = \,\alpha \beta \,\exp \,\left( { - \frac{{{x^2}}}{{\alpha kt}}} \right);\) where \(x\) is the distance, \(k\) is the Boltzmann constant and \(T\) is temperature and \(\alpha \) and \(\beta \) are two constants. The dimension of \(\beta \) is
Pick an option to check your answer.
Answer & Solution
Correct Answer
(B) \(M^2LT^{-4}\)
Step-by-step Solution
Detailed explanation
\(\begin{array}{l}
Power\,of\,e\,should\,be\,\dim ensionless.\\
So,\left[ \lambda \right] = \left( {\alpha Tk} \right)\\
\Rightarrow \,\,\,\,\,\,\,\,{L^2} = \left[ \alpha \right]\left( {M{L^2}{T^{ - 2}}} \right)\\
\Rightarrow \,\,\,\,\,\,\,\,\,\left( \alpha \right) = \left( {{M^{ - 1}}{T^2}} \right)\\
\Rightarrow \,\,\,\,\,\,\,\,\,\,\,E = \frac{1}{2}KT\\
\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\left( {M{L^2}{T^{ - 2}}} \right)\,\,;\,\,\left( E \right) = \left[ {KT} \right]\\
\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\left( {\alpha \beta } \right) = \left( F \right)\\
\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\,\left( {{M^{ - 1}}{T^2}} \right)\left( \beta \right) = \left( {ML{T^{ - 2}}} \right)
\end{array}\)
Power\,of\,e\,should\,be\,\dim ensionless.\\
So,\left[ \lambda \right] = \left( {\alpha Tk} \right)\\
\Rightarrow \,\,\,\,\,\,\,\,{L^2} = \left[ \alpha \right]\left( {M{L^2}{T^{ - 2}}} \right)\\
\Rightarrow \,\,\,\,\,\,\,\,\,\left( \alpha \right) = \left( {{M^{ - 1}}{T^2}} \right)\\
\Rightarrow \,\,\,\,\,\,\,\,\,\,\,E = \frac{1}{2}KT\\
\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\left( {M{L^2}{T^{ - 2}}} \right)\,\,;\,\,\left( E \right) = \left[ {KT} \right]\\
\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\left( {\alpha \beta } \right) = \left( F \right)\\
\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\,\left( {{M^{ - 1}}{T^2}} \right)\left( \beta \right) = \left( {ML{T^{ - 2}}} \right)
\end{array}\)
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