The speed of a wave is given by:
(1)
Where is the frequency and
the wavelength.
In the case of light, its speed is:
(2)
On the other hand, the described situation is known as Refraction, a phenomenon in which the light changes its direction when passing through a medium with a refractive index different from the other medium.
In this context, the Refractive index is a number that describes how fast light propagates through a medium or material, and is defined as the relation between the speed of light in vacuum (
) and the speed of light
in the second medium:
(3)
In addition, as the light changes its direction, its wavelength changes as well:
(4)
Knowing this, let's begin with the answers:
<h2>a) Frequency</h2>From equation (2) we can find :
(5)
Knowing that :
(6) >>>Frequency of the helium-neon laser light
We already know the wavelength of the light in air and the index of refraction of the glass.
So, we only have to find the wavelength in glass from equation (4):
(7) >>>Wavelength of the helium-neon laser light in glass
From equation (3) we can find the speed of this light in glass:
(8) >>>Speed of the helium-neon laser light in glass