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An electromagnetic wave of frequency v = 3.0 MHz passes from vacuum into a dielectric medium with permittivity ∈ = 4.0. Then ______.

#### Options

wave length is halved and frequency remains unchanged.

wave length is doubled and frequency becomes half.

wave length is doubled and the frequency remains unchanged.

wave length and frequency both remain unchanged.

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#### Solution

An electromagnetic wave of frequency v = 3.0 MHz passes from vacuum into a dielectric medium with permittivity ∈ = 4.0. Then **wave length is halved and frequency remains unchanged**.

**Explanation:**

During refraction Velocity of EM wave in hoover, frequency remains unchanged.

`"V"_"vacuum" = 1/(sqrt(mu_0∈_0)) = "c"`

`"v"_"med" = 1/(sqrt(mu_0∈_0xx4)) = "c"/2`

`lambda_"med"/lambda_"vacuum"= "v"_"med"/"v"_"vacuum"`

= `("c"//2)/"c"`

= `1/2`

∴ wave length is halved and frequency remains unchanged.

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