Can I see the book you read for I can answer and it more info because your question doesn’t make sense
Answer:

Explanation:
When an electromagnetic wave passes through the interface between two mediums, it undergoes refraction, which means that it bents and its speed and its wavelength change.
In particular, the wavelength of an electromagnetic wave in a certain medium is related to the index of refraction of the medium by:

where
is the wavelength in a vacuum (air is a good approximation of vacuum)
n is the refractive index of the medium
In this problem:
is the original wavelength of the wave
n = 1.47 is the index of refraction of corn oil
Therefore, the wavelength of the electromagnetic wave in corn oil is:

Answer:
2.1406 ×
m/sec
Explanation:
we know that energy is always conserved
so from the law of energy conservation

here V is the potential difference
we know that mass of proton = 1.67×
kg
we have given speed =50000m/sec
so potential difference 
now mass of electron =9.11×
so for electron

so the velocity of electron will be 2.1406×
m/sec
Answer:
The speed of light is that medium is 281907786.2 m/s.
Explanation:
since the critical angle is Фc = 430, we know that the refractive index is given by:
n = 1/sin(Фc)
= 1/sin(430)
= 1.06
then if n is the refractive index of the medium and c is the speed of light, then the speed of light in the medium is given by:
v = c/n
= (3×10^8)/(1.06)
= 281907786.2 m/s
Therefore, the speed of light is that medium is 281907786.2 m/s.