<h2>
Answers:</h2>
The speed of a wave is given by:
 (1)
  (1)
Where  is the frequency and
 is the frequency and   the wavelength.
 the wavelength.
In the case of light, its speed is:
 (2)
 (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 (
 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
) and the speed of light  in the second medium:
 in the second medium:
 (3)
 (3)
In addition, as the light changes its direction, its wavelength changes as well:
 (4)
 (4)
Knowing this, let's begin with the answers:
<h2>a) Frequency</h2>
From equation (2) we can find  :
:
 (5)
  (5)
Knowing that  :
:
 
  
 (6)   >>>Frequency of the helium-neon laser light
     (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.
 and the index of refraction of the glass. 
So, we only have to find the wavelength in glass  from equation (4):
 from equation (4):
 
 
 
 
 (7)   >>>Wavelength of the helium-neon laser light in glass
   (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:
of this light in glass:
 
 
 
 
 (8)  >>>Speed of the helium-neon laser light in glass
    (8)  >>>Speed of the helium-neon laser light in glass