The answer is reflection.
The drawing is simple but illustrates the concept beautifully.
<span>Electrons display some properties of waves and while they reside outside of the nucleus, their positions cannot be known with certainty. </span>
If friction is acting along the plane upwards
then in this case we will have
For equilibrium of 100 kg box on inclined plane we have
![mgsin\theta = F_f + T](https://tex.z-dn.net/?f=mgsin%5Ctheta%20%3D%20F_f%20%2B%20T)
also for other side of hanging mass we have
![T = Mg = 50(9.8) = 490 N](https://tex.z-dn.net/?f=T%20%3D%20Mg%20%3D%2050%289.8%29%20%3D%20490%20N)
now we have
![100(9.8)sin\theta = 100 + 490](https://tex.z-dn.net/?f=100%289.8%29sin%5Ctheta%20%3D%20100%20%2B%20490)
![980sin\theta = 590](https://tex.z-dn.net/?f=980sin%5Ctheta%20%3D%20590)
![sin\theta = 0.602](https://tex.z-dn.net/?f=sin%5Ctheta%20%3D%200.602)
![\theta = 37 degree](https://tex.z-dn.net/?f=%5Ctheta%20%3D%2037%20degree)
In other case we can assume that friction will act along the plane downwards
so now in that case we will have
![mgsin\theta + F_f = T](https://tex.z-dn.net/?f=mgsin%5Ctheta%20%2B%20F_f%20%3D%20T)
also we have
![T = Mg = 50(9.8) N](https://tex.z-dn.net/?f=T%20%3D%20Mg%20%3D%2050%289.8%29%20N)
now we have
![100(9.8)sin\theta + 100 = 50(9.8)](https://tex.z-dn.net/?f=100%289.8%29sin%5Ctheta%20%2B%20100%20%3D%2050%289.8%29)
![980sin\theta + 100 = 490](https://tex.z-dn.net/?f=980sin%5Ctheta%20%2B%20100%20%3D%20490)
![980 sin\theta = 490 - 100](https://tex.z-dn.net/?f=980%20sin%5Ctheta%20%3D%20490%20-%20100)
![sin\theta = 0.397](https://tex.z-dn.net/?f=sin%5Ctheta%20%3D%200.397)
![\theta = 23.45 degree](https://tex.z-dn.net/?f=%5Ctheta%20%3D%2023.45%20degree)
<em>So the range of angle will be 23.45 degree to 37 degree</em>
Answer:
The longest wavelength for closed at one end and open at the other is
y / 4 where y is the wavelength - that is node - antinode
The next possible wavelength is 3 y / 4 - node - antinode - node -antinode
y / 4 = 3 m y = 12 meters the longest wavelength
3 y / 4 = 3 m y = 4 meters 1 / 3 times as long