Answer:
The refractive index of the material is 1.28.
Explanation:
It is given that,
Refractive index of medium 1, n₁ = 1.31
Critical angle, 
At critical angle rays will reflects at 90 degrees. Using Snell's law as:

At critical angle, 



So, the refractive index of the material is 1.28. Hence, this is the required solution.
No. Beta particles are electrons.
To solve this problem it is necessary to apply the concept related to wavelength, specifically when the wavelength is observed from a source that is in motion to the observer.
By definition the wavelength is given defined by,

Where
= Observed wavelength
= Wavelength of the source
c = Speed of light in vacuum
u = Relative velocity of the source to the observer
According to our data we have that the wavelength emitted from the galaxy is 1875nm which is equal to the wavelength from the source, while the wavelength from the observer is 
Therefore replacing in the previous equation we have,




Solving for u,







Therefore the speed of the gas relative to earth is 0.02635 times the speed of light.
Answer:
The magnetic field strength is 0.29 T.
Explanation:
Given that,
Length of current-carrying wire, L = 52 cm = 0.52 m
Current, I = 15 A
Magnetic force, F = 2.3 N
We need to find the magnetic field strength. We know that the magnetic force is given by :

B is magnetic field strength

So, the magnetic field strength is 0.29 T.