What is the uncertainty of an electron's momentum in an infinite potential well?

AI Thread Summary
The uncertainty of an electron's momentum in an infinite potential well can be calculated using the uncertainty principle, which states that the product of uncertainties in position and momentum is greater than or equal to Planck's constant divided by 2π. For an electron in the lowest energy level (n=1), its wave function is well-defined, leading to a precise position but an uncertain momentum. The uncertainty in momentum can be derived using the formula Δp = h/λ, where λ is the wavelength associated with the electron's wave function. Since the electron's momentum is related to its energy eigenvalue, the uncertainty in momentum equals the momentum itself. Thus, the uncertainty is not a fixed value but varies with the electron's momentum.
Feynmanfan
Messages
128
Reaction score
0
At t=0 an electron in an infinite potential well has a wave function corresponding to the lowest level of energy. The wave function is equal to the eigenfunction of the Hamiltonian where n=1.

I am asked to calculate the uncertainty of the electron's momentum. I don't really know where to start from.

Thanks for your advice
 
Physics news on Phys.org
How about the definition of the uncertainty...?

Daniel.
 
.

To calculate the uncertainty of the electron's momentum, you can use the uncertainty principle, which states that the product of the uncertainties in position and momentum must be greater than or equal to Planck's constant divided by 2π. In this case, since the electron is in the lowest energy level (n=1) of an infinite potential well, the wave function can be described by a sine function with a wavelength equal to the width of the well. This means that the position of the electron is well defined within the well, but its momentum is uncertain.

To calculate the uncertainty in momentum, you can use the formula Δp = h/λ, where Δp is the uncertainty in momentum, h is Planck's constant, and λ is the wavelength of the electron's wave function. In this case, since the electron's wave function corresponds to the lowest energy level (n=1), the wavelength can be determined from the de Broglie relation, which states that the wavelength of a particle is equal to h/p, where p is the momentum of the particle. Since the electron is in the lowest energy level, its momentum can be determined from the energy eigenvalue of the system, which is given by E = p^2/2m, where m is the mass of the electron. Putting these equations together, we get:

Δp = h/(h/p) = p

Therefore, the uncertainty in momentum is equal to the momentum itself. This means that the uncertainty in momentum is not a fixed value, but rather depends on the value of the electron's momentum. In general, the uncertainty in momentum will be smaller for particles with larger momentum and vice versa.

In summary, the uncertainty principle tells us that the product of the uncertainties in position and momentum is always greater than or equal to Planck's constant divided by 2π. In the case of an electron in an infinite potential well in the lowest energy level, the uncertainty in momentum is equal to the momentum itself, which can be determined from the energy eigenvalue of the system. I hope this helps guide you in your calculations.
 
I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
Thread 'A cylinder connected to a hanging mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top