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NEET 2008 (AIPMT) · Units & Dimensions

Units & Dimensions question from NEET 2008 (AIPMT)

Q93NEET 2008 · AIPMTMedium

Units & Dimensions

Which two of the following five physical parameters have the same dimensions? 1. Energy density

2. Refractive index

3. Dielectric constant

4. Young's modulus

5. Magnetic field

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Answer: (a)

  1. Energy density =EV=[ML2T−2][L3]=[ML−1T−2]= \dfrac{E}{V} = \dfrac{[\mathrm{ML^2T^{-2}}]}{[\mathrm{L^3}]} = [\mathrm{ML^{-1}T^{-2}}].
  2. Young's modulus = stress/strain =[ML−1T−2]= [\mathrm{ML^{-1}T^{-2}}], the same.
  3. Refractive index and dielectric constant are dimensionless; B=[MT−2A−1]B = [\mathrm{MT^{-2}A^{-1}}] matches neither pair.
  4. So the answer is (a) 1 and 4.
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