Lithium has a work function of 290 eV Light having a wavelength of 1850 A us shi

Question

Lithium has a work function of 290 eV Light having a wavelength of 1850 A us shined on Li Determine the kinetic energy of the electron ejected Consider an electron confined to some finite system. The state of the electron is described by the wavefunction psi_(x) = squareroot2 sin k phi x, where k is some constant. Assume that the potential energy is zero, or V_(x) = 0. What is energy of the electron? The HF molecule has a harmonic vibrational frequency of 1.241 x 10^14 Hz. Determine its force constant using the reduced mass of HF Assume that the F atom doesn't move and that the vibration is due solely to the motion of the H atom. Using the mass of the H atom and the force constant just calculated, what is the expected frequency of the atom? (Mass of His 1.674 times 10^27 kg, (mass of F is 3.154 times 10^-26 kg)

Explanation / Answer

(4) According to Einstein's photo electric effect,

Energy lf light = Energy of electron (or work function) + K.E

But we know that, energy, E = h c / wave length

h c / wave length = work function + K.E

6.626 * 10-34 * 3 * 108 / 1850 * 10-10 = 2.90 * 1.602 * 10-19 + K.E

1.07 * 10-18 = 0.464 * 10-18 + K.E

therefore, K.E = (1.07 - 0.464) * 10-18 J

K.E = 6.06 * 10-19 J

K.E = 3.78 eV

NOTE:

h = Planck's constant = 6.626 * 10-34 J.s

c = speed of light = 3 * 108 m/s

1A0 = 10-8 cm = 10-10 m

1 eV = 1.602 * 10-19 J

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