The speed of an electron emitted from the surface of a sample of potassium by a photon is 668 kms-¹. What is the kinetic energy of the ejected electron?
To find the kinetic energy of the ejected electron, we can use the formula:
Kinetic energy (KE) = 0.5 * mass * velocity^2
The mass of an electron is approximately 9.11 x 10^-31 kg.
The velocity of the electron is 668 km/s = 668,000 m/s.
Plugging these values into the formula:
KE = 0.5 * 9.11 x 10^-31 kg * (668,000 m/s)^2
KE = 0.5 * 9.11 x 10^-31 kg * (4.46 x 10^11 m^2/s^2)
KE = 0.5 * 4.07 x 10^-19 kg m^2/s^2
KE = 2.035 x 10^-19 J
Therefore, the kinetic energy of the ejected electron is 2.035 x 10^-19 Joules.