Answer:
It is another machine that helps the main machine. Hope that helps!
Answer:
B.
Explanation: Mechanical waves need a medium to travel.
Answer:
The correct option is D
Explanation:
From the question we are told that
The refractive index of oil film is 
The thickness is 
Generally for constructive interference
![2t = [m + \frac{1}{2} ]* \frac{\lambda}{k}](https://tex.z-dn.net/?f=2t%20%20%3D%20%20%5Bm%20%20%2B%20%5Cfrac%7B1%7D%7B2%7D%20%5D%2A%20%20%5Cfrac%7B%5Clambda%7D%7Bk%7D)
For reflection of a bright fringe m = 1
=> ![2 * (290*10^{-9}) = [1 + \frac{1}{2} ]* \frac{\lambda}{1.48}](https://tex.z-dn.net/?f=2%20%2A%20%28290%2A10%5E%7B-9%7D%29%20%20%3D%20%20%5B1%20%20%2B%20%5Cfrac%7B1%7D%7B2%7D%20%5D%2A%20%20%5Cfrac%7B%5Clambda%7D%7B1.48%7D)
=> 
This wavelength fall in the range of a yellow light