The data listed below are for mechanical waves. Which wave has the greatest energy? amplitude = 7 cm; wavelength = 12 cm; period
2 answers:
Explanation :
The amplitude, wavelength and time period of three waves are given.
We know that energy of a wave is given by :
It is clear that energy of a wave is inversely proportional to the wavelength i.e
So, the wave having less wavelength will have the greatest energy.
Also, we know that energy of a wave is directly proportional to the square of amplitude i.e.
So, again the wave having maximum amplitude will have maximum energy.
Hence, the correct option is (C) i.e. "amplitude = 14 cm; wavelength = 7 cm; period = 12 seconds".
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0.042 moles of Hydrogen evolved
<h3>Further explanation</h3>Given
I = 1.5 A
t = 1.5 hr = 5400 s
Required
Number of Hydrogen evolved
Solution
Electrolysis of water ⇒ decomposition reaction of water into Oxygen and Hydrogen gas.
Cathode(reduction-negative pole) : 2H₂O(l)+2e⁻ ⇒ H₂(g)+2OH⁻(aq)
Anode(oxidation-positive pole) : 2H₂O(l)⇒O₂(g)+4H⁻(aq)+4e⁻
Total reaction : 2H₂O(l)⇒2H₂(g)+O₂(g)
So at the cathode H₂ gas is produced
Faraday : 1 mole of electrons (e⁻) contains a charge of 96,500 C
Q = i.t
Q = 1.5 x 5400
Q = 8100 C
mol e⁻ = 8100 : 96500 = 0.084
From equation at cathode , mol ratio e⁻ : H₂ = 2 : 1, so mol H₂ = 0.042