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An electron with energy 13.2 eV collides with an element, and the electron emerges with energy 4.5 eV. What wavelength of light would also be emitted along with the electron?

Sagot :

Answer: [tex]140\ nm[/tex]

Explanation:

Given

Initial kinetic energy is [tex]K_i=13.2\ eV[/tex]

Final kinetic energy is [tex]K_f=4.5\ eV[/tex]

Change in kinetic energy is [tex]\Delta K=K_i-K_f[/tex]

[tex]\Rightarrow \Delta K=13.2-4.5\\\Rightarrow \Delta K=8.7\ eV[/tex]

Energy is given by

[tex]E=\dfrac{hc}{\lambda}[/tex]

Equate it to change in kinetic energy

[tex]\Rightarrow 8.7=\dfrac{hc}{\lambda}\\\\\Rightarrow \lambda =\dfrac{6.63\times 10^{-34}\times 3\times 10^8}{8.7\times 1.6\times 10^{-19}}\\\\\Rightarrow \lambda =1.4\times 10^{-7}\ m\\\Rightarrow \lambda=140\ nm[/tex]

Therefore, the wavelength associated with it is [tex]140\ nm[/tex].