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NEETPhysicsElectromagnetic Waves

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): The ratio of the amplitude of the electric field to the magnetic field ( E₀/B₀ ) decreases when a plane electromagnetic wave enters a non-magnetic dielectric medium from vacuum. Reason (R): The speed of the electromagnetic wave decreases in the dielectric medium, and the ratio E₀/B₀ is equal to the

Options

  1. ABoth Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A)
  2. BBoth Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A)
  3. CAssertion (A) is true but Reason (R) is false
  4. DAssertion (A) is false but Reason (R) is true

Correct answer

B. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A)

Step-by-step solution

The ratio of the amplitude of the electric field ( E₀ ) to the magnetic field ( B₀ ) in any medium is equal to the speed of the electromagnetic wave ( v ) in that medium, i.e., E₀ B₀ = v . When an electromagnetic wave enters a dielectric medium from vacuum, its speed decreases from c to v = c n , where n > 1 is the refractive index of the medium. Since the speed v decreases, the ratio E₀ B₀ also decreases. Therefore, both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A). Answer

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