Answer:
Heliocentrism is the astronomical model in which the Earth and planets revolve around the Sun at the center of the Universe.
Explanation:
Answer:

Explanation:
It is given that,
Initially, the electron is in n = 7 energy level. When it relaxes to a lower energy level, emitting light of 397 nm. We need to find the value of n for the level to which the electron relaxed. It can be calculate using the formula as :


R = Rydberg constant, 

Solving above equation we get the value of final n is,

or

So, it will relax in the n = 2. Hence, this is the required solution.
<h3>The metre is the length of the path travelled by light in vacuum during a time interval of 1299 792 458 of a second.</h3>
Answer:
Explanation:
Given
mass m collides elastically with floor and jump to its original height I .e.velocity of rebound is same as the initial velocity
Impulse imparted by steel ball to the ground is given by the change in momentum of steel ball

and impulse is product of average force and time
so we need time to calculate the average force. So, option e is correct
Growing grass plants and trees is the easiest and best way to prevent flood waters from running off too quickly causing further soil erosion. <span />