Answer: 
Explanation:
Given
Cross-sectional area of wire 
Extension of wire 
Extension in a wire is given by

where, 

for same force, length and material

Divide (i) and (ii)

1. Frequency: 
The frequency of a light wave is given by:

where
is the speed of light
is the wavelength of the wave
In this problem, we have light with wavelength

Substituting into the equation, we find the frequency:

2. Period: 
The period of a wave is equal to the reciprocal of the frequency:

The frequency of this light wave is
(found in the previous exercise), so the period is:

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<h3 /><h3><em>S</em><em>m</em><em>a</em><em>l</em><em>l</em><em> </em><em>Explanation</em><em>:</em><em>-</em></h3>
The reactants are charcoal that is unlit + oxygen and the products are the burnt charcoal + energy.
(Explanation with formula and reason attached. Check it.)

I think it’s 8 hours. I’m sorry if I’m wrong.
I just did 400 divided by 50
The correct answer among the choices given is option B. The energy transformation that occurs in the core of a nuclear reactor is from nuclear energy to thermal energy. In a power plant nuclear fission which involves nuclear energy to heat up water around it. This part is the core of the process.