1 mile. Is this a joke lol
Kinetic energy and potential energy pair is the quantity in which one will increase then other will decrease
As we know that sum of kinetic energy and potential energy will always remain conserved
So here we will have

so here as we move away from mean position the kinetic energy will decrease while at the same time potential energy will increase.
So the pair of potential energy and kinetic energy will satisfy the above condition
Velocity = fλ
where f is frequency in Hz, and λ is wavelength in meters.
2.04 * 10⁸ m/s = 5.09 * 10¹⁴ Hz * λ
(2.04 * 10⁸ m/s) / (5.09 * 10¹⁴ Hz ) = λ
4.007*10⁻⁷ m = λ
The wavelength of the yellow light = 4.007*10⁻⁷ m
I’m just a answering for points sorry