The unit of \( \mu_0\varepsilon_0 \) is
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \( \mathrm{s^{2}\,m^{-2}} \)
The speed of electromagnetic waves in vacuum is \( c=1/\sqrt{\mu_0\varepsilon_0} \), so \( \mu_0\varepsilon_0=1/c^{2} \) and its unit is the inverse square of the unit of speed.
\( \begin{aligned} \text{Unit of }\mu_0\varepsilon_0 &= \frac{1}{(\mathrm{m\,s^{-1}})^{2}} \\ &= \frac{1}{\mathrm{m^{2}\,s^{-2}}} \\ &= \mathrm{s^{2}\,m^{-2}} \end{aligned} \)
NCERT (2026-27):
Summary – “5. The speed c of electromagnetic wave in vacuum is related to μ0 and ε0 (the free space permeability and permittivity constants) as follows:
\( c=1/\sqrt{\mu_0\varepsilon_0} \)
The value of c equals the speed of light obtained from optical measurements.”