Answer:
emitted intensity is 7.48 10⁸ 8 W / m²
Explanation:
To calculate this energy, let's start by using the win displacement law, and the Planck equation
λ T = 2,898 10-3 m K
E = h f
c = f λ
E = h c /λ
λ = hc / E
calculate
(h c / E) T = 2,898 10⁻³
T = 2,898 10⁻³ E / h c
E = 4 eV (1.6 10⁻¹⁹ J / 1eV) = 6.4 10⁻¹⁹ J
T = 2,898 10⁻³ 6.4 10⁻¹⁹ / (6,626 10⁻³⁴ 3 10⁸)
T = 18.54 10⁻²² / (19.878 10⁻²⁶)
T = 0.9331 10⁴ K
Having the temperature at which the emission occurs we can use Stefan's law
P = σ A e T⁴
The constant σ = 5.670 10⁻⁸ W / m² K⁴, e is the emissivity for a black body worth 1
P / A = 5,670 10⁻⁸ 1 (0.9331 10⁴)⁴
P / A = 7.48 10⁸ 8 W / m²
