Question

A beam of light, with a wavelength of 4170 Å, is shined on sodium, which has a work function (binding energy) of 4.41 × 10 –19 J. Calculate the kinetic energy and speed of the ejected electron.

Answer 1

Step-by-step explanation:

Given that,

Wavelength of the light,
`\lambda=4170\ A=4170* 10^(-10)\ m`

Work function of sodium,
`W_o=4.41* 10^(-19)\ J`

The kinetic energy of the ejected electron in terms of work function is given by :

`KE=h(c)/(\lambda)-W_o\\\\KE=6.63* 10^(-34)* (3* 10^8)/(4170* 10^(-10))-4.41* 10^(-19)\\\\KE=3.59* 10^(-20)\ J`

The formula of kinetic energy is given by :

`KE=(1)/(2)mv^2\\\\v=\sqrt{(2KE)/(m)} \\\\v=\sqrt{(2* 3.59* 10^(-20))/(9.1* 10^(-31))} \\\\v=2.8* 10^5\ m/s`

Hence, this is the required solution.