True it only changes form. Like when water evaporates goes from liquid to a gas and is not destroyed.
When person is observing destructive interference at 0.20 m distance from the equidistant position then we can say that path difference must be equal to half of the wavelength
now we will have

now we know that
y = 0.20 m
d = 2.4 m
L = 10 m
now here we have


now frequency of wave is given as


Answer:
There's a video called Drawing Position vs Time Graphs made by MrDGenova that may help you, it's only three minutes long.
Explanation:
Hope that helps, if not, you could tell me what you don't understand and I could try explaining it in further detail.
Answer:
B
Explanation:
Momentum is the product or multiplication of a body's mass and its speed.
Since all options have the mass and speed in the same units, there is no need for conversion.
A. 20 x 500 = 10000, B. 200 x 60 = 12000
The same goes for the rest!