Introduction:
The momentum of an electron can be determined using the de Broglie wavelength associated with it. The de Broglie wavelength is given by the equation λ = h/p, where λ is the wavelength, h is Planck's constant, and p is the momentum. In this problem, we are given that the momentum of the electron changes by 'P' and the de Broglie wavelength associated with it changes by 0.50%. We need to find the initial momentum of the electron.

Given:
Change in momentum, ΔP = P
Change in wavelength, Δλ/λ = 0.50%

Calculating the initial momentum:
To find the initial momentum of the electron, we can use the equation for the de Broglie wavelength and the given information about the change in momentum and wavelength.

We know that the de Broglie wavelength is inversely proportional to the momentum. Therefore, if the wavelength changes by 0.50%, the momentum must change by the same percentage.

Let the initial momentum be p0 and the initial wavelength be λ0.
The change in momentum is given by:
ΔP = p - p0

Given that the change in momentum is equal to 'P', we have:
P = p - p0

Since the change in wavelength is given by:
Δλ/λ = 0.50%

We can write the equation for the change in wavelength as:
Δλ/λ = (λ - λ0)/λ0

Rearranging the equation, we get:
(λ - λ0)/λ0 = 0.50%

Simplifying further, we have:
λ - λ0 = 0.50% * λ0
λ - λ0 = 0.005λ0

Now, substituting the equation for wavelength in terms of momentum, we have:
(λ0 * p0)/h - λ0 = 0.005λ0

Simplifying further, we get:
p0 = (0.005λ0 * h)/(λ0 - h)

Conclusion:
The initial momentum of the electron can be calculated using the equation p0 = (0.005λ0 * h)/(λ0 - h), where λ0 is the initial wavelength and h is Planck's constant.