Answer:
2.When they reach the bottom of the fall
Explanation:
The potential energy of the waterfall is maximum at the maximum height and decreases with decrease in height. Based on the law of conservation of mechanical energy, as the potential energy of the water fall is decreasing with decrease in height of the fall, its kinetic energy will be increasing and the kinetic energy will be maximum at zero height (bottom of the fall).
Thus, the correct option is "2" When they reach the bottom of the fall
However instead of crests and troughs, longitudinal waves have compressions and rarefactions. Compression. A compression is a region in a longitudinal wave where the particles are closest together. Rarefaction. A rarefaction is a region in a longitudinal wave where the particles are furthest apart.
Lower resistivity means higher conductivity: among these materials, the best conductor is silver, therefore it must be the material with lowest resistivity among those. We can also have a look at the value of resistivity of the different materials listed in the problem, to check our answer. The resistivities of the materials are the following:
Wood:

Salt water:

Silver:

Lead:

<span>We see that the material with lowest resistivity among those is silver, therefore the correct answer is silver.</span>
The deflection angle is 37.29º if the prism was made of polystyrene plastic.
What is a laser beam?
Laser beam is a light beam propagating dominantly in one direction.
It is a beam of radiation produced from a laser.
Here given that,
refraction index of glass, n1= 1.52
refraction index of polystyrene plastic, n2 = 1.59
deflection angle, B = 22.6º
For the second surface,
B = 45º - 22.6º
B = 22.40º
Now from the formula of Snell's law:
n1 sinФ = n2 sin B
sin B / sinФ = n1 / n2
sinФ = (sin 22.40º) * ( 1/ 1.59)
Ф = 37.29º
Hence,
The deflection angle is 37.29º if the prism was made of polystyrene plastic.
Learn more about laser beam here:
<u>brainly.com/question/4218151</u>
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