9.01 × 10⁻²⁶ J
Step-by-step explanation
ΔE = h · f
Where
- ΔE the change in energy,
- h the planck's constant, and
- f frequency of the emission.
However, only λ is given.
f = c / λ
Where
- f frequency of the emission,
- λ wavelength of the emission, and
- c the speed of light.
For this emission:
f = 2.998 × 10⁸ / 2.21 = 1.36 × 10⁸ s⁻¹.
ΔE = h · f = 6.626 × 10⁻³⁴ × 1.36 × 10⁸ = 9.01 × 10⁻²⁶ J