Answer:
sorry I hate when people press your question and answer with a fake answer for points, however you said it was 100 points and it's not even close lol but it is "your speed Is constant" that is not true
Answer:
The value is 
Explanation:
From the question we are told that
The wavelength of the beam is 
The refractive index is 
Generally from the condition for destructive interference the depth of the pit is mathematically represented as
![t = [ m + \frac{1}{2} ] * \frac{\lambda}{n_r} * \frac{1}{2}](https://tex.z-dn.net/?f=t%20%20%3D%20%5B%20m%20%20%2B%20%5Cfrac%7B1%7D%7B2%7D%20%5D%20%2A%20%20%5Cfrac%7B%5Clambda%7D%7Bn_r%7D%20%20%2A%20%20%5Cfrac%7B1%7D%7B2%7D)
Here m which is the order of the fringe is zero because both beams cancel out
So
![t = [ 0 + \frac{1}{2} ] * \frac{790 *10^{-9}}{ 1.80} * \frac{1}{2}](https://tex.z-dn.net/?f=t%20%20%3D%20%5B%200%20%20%2B%20%5Cfrac%7B1%7D%7B2%7D%20%5D%20%2A%20%20%5Cfrac%7B790%20%2A10%5E%7B-9%7D%7D%7B%201.80%7D%20%20%2A%20%20%5Cfrac%7B1%7D%7B2%7D)
=> 
=>
An isotope is one of 2+ types of the same element, which will have the same number of protons but a different number of neutrons in its nucleus. This means that the relative atomic mass may be different among isotopes, but the chemical properties will remain the same. Isotopes are usually found in radioactive forms of an element.
