Question

When electromagnetic waves are allowed to pass through a glass slab, then

• A. velocity of the waves remains constant but frequency changes
• B. frequency and wavelength of waves remain constant but its velocity changes
• C. frequency of the waves remains constant but wavelength changes
• D. velocity remains constant but wavelength changes

Answer 1

The correct option is C

frequency of the waves remains constant but wavelength changes

Velocity-frequency-wavelength relation:

The velocity ($v$), frequency ($\nu$) and wavelength ($\lambda$) of an electromagnetic wave are related as follows:

$v=\nu \times \lambda$

1. The frequency ($\nu$) of a wave is an intrinsic property, i.e., the frequency of the wave remains the same in all mediums and depends only on the wave source.
2. Now, we know that the velocity ($v$) of an electromagnetic wave in glass is different from the velocity in the air.
3. From the equation of velocity, it is clear that wavelength will also change in the glass.

Hence, the correct option is (c).