I think it's true
I'm not really sure
Answer:
Explanation:
The energy of a photon is given by the equation
, where h is the <em>Planck constant</em> and f the frequency of the photon. Thus, N photons of frequency f will give an energy of
.
We also know that frequency and wavelength are related by
, so we have
, where c is the <em>speed of light</em>.
We will want the number of photons, so we can write

We need to know then how much energy do we have to calculate N. The equation of power is
, so for the power we have and considering 1 second we can calculate the total energy, and then only consider the 4% of it which will produce light, or better said, the N photons, which means it will be
.
Putting this paragraph in equations:
.
And then we can substitute everything in our equation for number of photons, in S.I. and getting the values of constants from tables:

The density of silver is ρ = 10500 kg/m³ approximately.
Given:
m = 1.70 kg, the mass of silver
t = 3.0 x 10⁻⁷ m, the thickness of the sheet
Let A be the area.
Then, by definition,
m = (t*A)*ρ
Therefore
A = m/(t*ρ)
= (1.7 kg)/ [(3.0 x 10⁻⁷ m)*(10500 kg/m³)]
= 539.7 m²
Answer: 539.7 m²