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

1. wave length is halved and frequency remains unchanged
2. wave length is doubled and frequency becomes half
3. wave length is doubled and frequency remains unchanged
4. wave length and frequency both remain unchanged

Correct answer: wave length is halved and frequency remains unchanged

Solution

When an electromagnetic wave enters a dielectric medium, its speed decreases due to the medium's permittivity, which results in a shorter wavelength. However, the frequency of the wave remains constant as it transitions between media.

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