JEE Mains · Physics · STD 11 - Units,dimensions and measurement
- JEE Mains 2026
- Hard
- MCQ
Match List-I with List-II.
| List-I | List-II |
|---|---|
| A. Meter (L) | I. \(\sqrt{\dfrac{hc}{G}}\) |
| B. Second (S) | II. \(\sqrt{\dfrac{Gh}{c^5}}\) |
| C. Kilogram (M) | III. \(\sqrt{\dfrac{K^2L^2c^3}{Gh}}\) |
| D. Kelvin (K) | IV. \(\sqrt{\dfrac{Gh}{c^3}}\) |
where \(h\) (Planck's constant), \(G\) (gravitational constant) and \(c\) (speed of light in vacuum) as fundamental units.
Choose the correct answer from the options given below :
Pick an option to check your answer.
Answer & Solution
Correct Answer
(B) A-IV, B-II, C-I, D-III
Step-by-step Solution
Detailed explanation
The dimensional formulas for the given fundamental constants are:
\([h] = M L^2 T^{-1}\)
\([c] = L T^{-1}\)
\([G] = M^{-1} L^3 T^{-2}\)
Evaluating the dimensions of the expressions in List-II:
For I: \(\sqrt{\dfrac{hc}{G}} = \sqrt{\dfrac{(M L^2 T^{-1})(L T^{-1})}{M^{-1} L^3 T^{-2}}} = \sqrt{M^2} = M\) (Kilogram).
Thus, C \(\rightarrow\) I.
For II: \(\sqrt{\dfrac{Gh}{c^5}} = \sqrt{\dfrac{(M^{-1} L^3 T^{-2})(M L^2 T^{-1})}{(L T^{-1})^5}} = \sqrt{\dfrac{L^5 T^{-3}}{L^5 T^{-5}}} = \sqrt{T^2} = T\) (Second).
Thus, B \(\rightarrow\) II.
For IV: \(\sqrt{\dfrac{Gh}{c^3}} = \sqrt{\dfrac{(M^{-1} L^3 T^{-2})(M L^2 T^{-1})}{(L T^{-1})^3}} = \sqrt{\dfrac{L^5 T^{-3}}{L^3 T^{-3}}} = \sqrt{L^2} = L\) (Meter).
Thus, A \(\rightarrow\) IV.
For III: Substituting \(L^2 = \dfrac{Gh}{c^3}\) from IV into the expression gives \(\sqrt{\dfrac{K^2 L^2 c^3}{Gh}} = \sqrt{K^2 \left(\dfrac{Gh}{c^3}\right) \dfrac{c^3}{Gh}} = \sqrt{K^2} = K\) (Kelvin).
Thus, D \(\rightarrow\) III.
The correct matching is A-IV, B-II, C-I, D-III.
Answer: A-IV, B-II, C-I, D-III
\([h] = M L^2 T^{-1}\)
\([c] = L T^{-1}\)
\([G] = M^{-1} L^3 T^{-2}\)
Evaluating the dimensions of the expressions in List-II:
For I: \(\sqrt{\dfrac{hc}{G}} = \sqrt{\dfrac{(M L^2 T^{-1})(L T^{-1})}{M^{-1} L^3 T^{-2}}} = \sqrt{M^2} = M\) (Kilogram).
Thus, C \(\rightarrow\) I.
For II: \(\sqrt{\dfrac{Gh}{c^5}} = \sqrt{\dfrac{(M^{-1} L^3 T^{-2})(M L^2 T^{-1})}{(L T^{-1})^5}} = \sqrt{\dfrac{L^5 T^{-3}}{L^5 T^{-5}}} = \sqrt{T^2} = T\) (Second).
Thus, B \(\rightarrow\) II.
For IV: \(\sqrt{\dfrac{Gh}{c^3}} = \sqrt{\dfrac{(M^{-1} L^3 T^{-2})(M L^2 T^{-1})}{(L T^{-1})^3}} = \sqrt{\dfrac{L^5 T^{-3}}{L^3 T^{-3}}} = \sqrt{L^2} = L\) (Meter).
Thus, A \(\rightarrow\) IV.
For III: Substituting \(L^2 = \dfrac{Gh}{c^3}\) from IV into the expression gives \(\sqrt{\dfrac{K^2 L^2 c^3}{Gh}} = \sqrt{K^2 \left(\dfrac{Gh}{c^3}\right) \dfrac{c^3}{Gh}} = \sqrt{K^2} = K\) (Kelvin).
Thus, D \(\rightarrow\) III.
The correct matching is A-IV, B-II, C-I, D-III.
Answer: A-IV, B-II, C-I, D-III
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