<h2>
Answers:</h2>
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
<h2>b) Wavelength in glass</h2>
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
<h2>c) Speed in glass</h2>
From equation (3) we can find the speed of this light in glass:
(8) >>>Speed of the helium-neon laser light in glass
