I think it occurs whenever waves come together so that they are in phase with each other.
Answer:
The moment of inertia is 
Explanation:
From the question we are told that
The frequency is 
The mass of the pendulum is 
The location of the pivot from the center is 
Generally the period of the simple harmonic motion is mathematically represented as

Where I is the moment of inertia about the pivot point , so making I the subject of the formula it
=> ![I = [ \frac{T}{2 \pi } ]^2 * m* g * d](https://tex.z-dn.net/?f=I%20%3D%20%20%5B%20%5Cfrac%7BT%7D%7B2%20%5Cpi%20%7D%20%5D%5E2%20%2A%20%20m%2A%20%20g%20%2A%20d)
But the period of this simple harmonic motion can also be represented mathematically as

substituting values


So
![I = [ \frac{2.174}{2 * 3.142 } ]^2 * 2.40* 9.8 * 0.380](https://tex.z-dn.net/?f=I%20%3D%20%20%5B%20%5Cfrac%7B2.174%7D%7B2%20%2A%203.142%20%7D%20%5D%5E2%20%2A%20%20%202.40%2A%20%209.8%20%2A%200.380)

When the core of a star like the sun uses up its supply of hydrogen for fusion, the core begins to contract in size. The gravitational forces becomes strong and cause the star to reduce in size. as the star contracts, the temperature of the star also rises since the heat is distributed inside smaller Volume now.