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## Homework Statement

The work function of chromium metal is 7.2 x 10

^{-19}J. What is the maximum speed an electron can be moving if it is ejected from chromium metal by light of wavelength 250 nm? (Answer: u= 4 x10

^{5}m/s)

## Homework Equations

[tex]\Phi = h v_{0}[/tex]

[tex]KE = h v_{light} - \Phi = \frac{m_{e} u^{2}_{e}}{2}[/tex]

[tex]\Delta E_{light}= \Phi + KE[/tex]

[tex]h[/tex] is Planck's constant

[tex]v_{0}[/tex] is the characteristic frequency

[tex]m_e[/tex] is the mass of an electron (9.1 x 10

^{-31}kg)

[tex]u_e[/tex] is the speed of the electron

## The Attempt at a Solution

[tex]7.2\times10^{-19} J = \frac{(9.1\times10^{-31} kg) (u^{2}_{e})}{2}[/tex]

[tex]u_e \approx 1.3 \times 10^6 m/s[/tex]

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