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 ______ × 10-2 cm. - Physics (JEE Main)

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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 ______ × 10-2 cm. 


  • 167

  • 367

  • 667

  • 967



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 667 × 10-2 cm. 


Wavelength of EM wave λv in vacuum

= `"c"/"f"=(3xx10^8)/(3xx10^9)` = 0.1 m

∴ Wavelength of EM wave λm in medium = `0.1/mu`

 Where µ is refractive index given by,

µ = `sqrt(mu_"r"epsilon_"r")`

Assuming material to be non-magnetic,

µr = 1

∴ µ = `sqrt(1xx2.25)` = 1.5

λ= `0.1/1.5 = 1/15`m

= 6.67 cm 

= 667 × 10-2 cm. 

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