Through what potential difference ΔV must electrons be accelerated (from rest) so that they will have the same wavelength as an x-ray of wavelength 0.150 nm ? Use 6.63×10−34 J⋅s for Planck's constant, 9.11×10−31 kg for the mass of an electron, and 1.60×10−19 C for the charge on an electron. Express your answer using three significant figures.

Respuesta :

Answer:

66.3 V

Explanation:

The wavelength of the electron must be equal to that of the x-ray photon:

[tex]\lambda=0.150 nm=0.15\cdot 10^{-9}m[/tex]

the De Broglie wavelength of the electron is related to its momentum, p, by the formula

[tex]p=\frac{h}{\lambda}[/tex]

where h is the Planck constant. Solving the formula, we find

[tex]p=\frac{6.63\cdot 10^{-34} Js}{0.15\cdot 10^{-9}m}=4.4\cdot 10^{-24} kg m/s[/tex]

Now we can find the electron's energy using the formula

[tex]E=\frac{p^2}{2m}=\frac{(4.4\cdot 10^{-24} kg m/s)^2)}{2(9.11\cdot 10^{-31} kg)}=1.06\cdot 10^{-17} J[/tex]

Then, we know that the energy of an electron accelerated through a potential difference of [tex]\Delta V[/tex] is

[tex]E=q\Delta V[/tex]

where

[tex]q=1.60\cdot 10^{-19} C[/tex] is the electron charge

Solving the equation for the potential difference, we find

[tex]\Delta V=\frac{E}{q}=\frac{1.06\cdot 10^{-17} J}{1.60\cdot 10^{-19} C}=66.3 V[/tex]