Question

Photoelectrons with a maximum speed of 7.00 · 105 m/s are ejected from a surface in the presence of light with a frequency of 8.00 · 1014Hz. If the mass of an electron is 9.1 · 10-31 kg, calculate the maximum kinetic energy of a single electron, in joules.
_____ J


6.3 x 10-25
4.4 x 10-19
3.2 x 10-25
2.2 x 10-19

Answer 1

This is just testing your ability to recall that kinetic energy is given by: 

k.e. = ½mv² 

where m is the mass and v is the velocity of the particle. 

The frequency of the light is redundant information. 

Here, you are given m = 9.1 * 10^-31 kg and v = 7.00 * 10^5 m/s. 
Just plug in the values: 

k.e. = ½ * 9.1 * 10^-31 * (7.00 * 10^5)² 
k.e. = 2.23 * 10^-19 J 
so it will be d:2.2*10^-19 J