Answer:
N = 6.4886 *10¹²
Explanation:
Assumption:
2.5% of electrical energy is converted into light.
Power = 100W
So, to calculate energy of light per scoend, wee simply multiply 100 to 2.5%
E = 100 * (2.5/100) = 2.5J
To calculate number of photons, we have formula
N = (2.5 * λ)/hc
Now, using distance of 5m, we find area of sphere using formula 4λR²
A=4*3.14*5² = 314m²
Now, to determine number of photons passing through area of 3cm² or 0.0003m²
N = (3*10⁻⁴/314)*[(2.5*λ)/hc]
Now by putting the values we gett,
N = (3*10⁻⁴/314)*[(2.5*540*10⁻⁹)/((6.626*10⁻³⁴J.s)(3*10⁸))]
N = 6.4886 *10¹²
