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JEE Main 2021 (24 Feb, Shift 2) · Speed of EM Waves in a Medium

Speed of EM Waves in a Medium question from JEE Main 2021 (24 Feb, Shift 2)

Q19JEE Main 2021 · 24 FEB · SHIFT 2Easy

Speed of EM Waves in a Medium

An electromagnetic wave of frequency 3 GHz enters a dielectric medium of relative electric permittivity 2.25 from vacuum. The wavelength of this wave in that medium will be _________ ×\times 10−-2 cm.

Numerical answer type. Work it out, then open the answer.

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Answer: 667

  1. In vacuum λ0=c/ν=3×1083×109=0.1\lambda_0 = c/\nu = \dfrac{3 \times 10^{8}}{3 \times 10^{9}} = 0.1 m =10= 10 cm.
  2. n=εr=2.25=1.5n = \sqrt{\varepsilon_r} = \sqrt{2.25} = 1.5
  3. λ=λ0/n=10/1.5=6.67\lambda = \lambda_0/n = 10/1.5 = 6.67 cm =667×10−2= 667 \times 10^{-2} cm
  4. So the answer is 667.
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