Q73 / 90 · JEE Main 2022 (25 Jun Shift 2) · Physics

The electromagnetic waves travel in a medium at a speed of 2.0×108 m s-1. The relative permeability of the medium is 1.0. The relative permittivity of the medium will be

  • Correct answer
    A
    2.25
  • B
    4.25
  • C
    6.25
  • D
    8.25

Solution

Here, v=2×108 m s−1 and μr=1

The speed of electromagnetic waves in a medium is given by v=1με  ...i

where μ and ε are absolute permeability and absolute permittivity of the medium.
Now, μ=μ0μr and ε=ε0εr
Then, we have, 

v=1μ0μr×ε0εr=1μ0ε0×1μrεr=cμrεr

orεr=c2v2μr=3×10822×1082=94=2.25

Hence, the correct answer is option: 'A'.

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