Photoelectrons with a maximum speed of 6.50 x 107 m/s are ejected from a surface in the presence of light with a frequency of 6.75 x 1014hz. if the mass of an electron is 9.10 x 10-31 kg, calculate in joules the maximum kinetic energy of a single electron. 3.84 x 10-15 j 1.92 x 10-15 j 5.92 x 10-23 j 3.07 x 10-16 j

Correct choice is

1.92 x 10⁻¹⁵ J

Explanation:

m = mass of electron = 9.1 x 10⁻³¹ kg

v = maximum speed of electron ejected from the surface = 6.50 x 10⁷ m/s

KE = maximum kinetic energy of electron

maximum kinetic energy is given as

KE = (0.5) m v²

inserting the above values

KE = (0.5) (9.1 x 10⁻³¹ ) (6.50 x 10⁷ )²

KE = (4.55 x 10⁻³¹ ) (6.50 x 10⁷ )²

KE = (4.55 x 10⁻³¹ ) (42.25 x 10¹⁴)

KE = 1.92 x 10⁻¹⁵ J

e/c, where e is its total energy