Ray Optics

JEE Main level, single correct, medium

70 of 295

Question 70 of 295

This question has Statement-1 and Statement-2. Of the four choices given after the Statements, choose the one that best describes the two Statements.
Statement-1: Short wave transmission is achieved due to the total internal reflection of the e-m wave from an appropriate height in the ionosphere.
Statement-2: Refractive index of a plasma is independent of the frequency of e-m waves.

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Answer: (A) Statement-1 is true, Statement- 2 is false.

Effective refractive index of the ionosphere
neff=n0[1−80.5 Nf2]1/2\mathrm{n}_{\mathrm{eff}}=\mathrm{n}_0\left[1-\frac{80.5 \mathrm{~N}}{\mathrm{f}^2}\right]^{1 / 2}
where f\mathrm{f} is the frequency of em waves

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