Answer:
1.59 x 10⁻²⁵ J.
Explanation:
E = h ν , where
E is the energy of the photon,
h is Planck's constant (h = 6.626 x 10 ⁻³⁴ J.s)
ν is the frequency of the photon
λ.ν = c,
where c is the speed of light in vacuum (c = 3 .0 x 10 ⁸ m/s).
λ = 125 cm = 1.25 m.
Now, E = h.c/λ.
∴ E = h.c/λ = (6.626 x 10 ⁻³⁴ J.s) (3 .0 x 10 ⁸ m/s) / (1.25 m) = 1.59 x 10⁻²⁵ J.
