The cutoff frequency for magnesium is 8.93 x 10¹⁴ Hz.
<h3>What is cutoff frequency?</h3>
The work function is related to the frequency as
W0 = h x fo
where, fo = cutoff frequency and h is the Planck's constant
Given is the work function for magnesium is 3.70 eV.
fo = 3.7 x 1.6 x 10⁻¹⁹ / 6.626 x 10⁻³⁴
fo = 8.93 x 10¹⁴ Hz.
Thus, the cut off frequency is 8.93 x 10¹⁴ Hz.
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The first one would be thermal energy
Answer:

Explanation:
Given the following data;
Frequency = 4.0 x 10⁹ Hz
Planck's constant, h = 6.626 x 10-34 J·s.
To find the energy of the electromagnetic wave;
Mathematically, the energy of an electromagnetic wave is given by the formula;
E = hf
Where;
E is the energy possessed by a wave.
h represents Planck's constant.
f is the frequency of a wave.
Substituting the values into the formula, we have;


Power = 1800W (or 1.8KW by dividing by 1000)
Time = 3 hours
Power = energy/ time
1.8KW = energy/ 3
x3
5.4Kw/h= energy
(5.4KJ or 5400J used)
$0.15 Kw/h
$0.15 X 5.4 = 0.81
Thus, cost $0.81
Hope this helps!