Light of frequency 7.21 × 1014 Hz is incident on a metal surface.Electrons with a maximum speed of 6.0 × 105 m/s are ejected fromthe surface. What is the threshold frequency for photoemission ofelectrons?
Given: The frequency of the incident light is 7.21 × 10 14 Hz and the maximum speed of electrons is 6 .0 × 10 5 m / s .
The threshold frequency can be calculated as,
h ν = h ν 0 + 1 2 m v 2 ν 0 = ν − m v 2 2 h
Where, the mass of electron is m , Planck constant is h , ν is the frequency of incident light, ν 0 is the threshold frequency and v is the maximum speed of ejected electrons.
By substituting the given values in the above equation, we get ν 0 = 7.21 × 10 14 − ( 9.1 × 10 − 31 ) × ( 6 × 10 5 ) 2 2 × 6.626 × 10 − 34 = 7.21 × 10 14 − 2.472 × 10 14 = 4.738 × 10 14 Hz
Thus, the threshold frequency for the photo emission of electrons is 4.738 × 10 14 Hz .
Given: The frequency of the incident light is
The threshold frequency can be calculated as,
Where, the mass of electron is
By substituting the given values in the above equation, we get
Thus, the threshold frequency for the photo emission of electrons is
