A4.A photon with an energy of 13.6eV knocks an electron out of a hydrogen atom.The kinetic energy of the ejected electron is equal to __ eV. 1. 13.6 2.3.4 3. 10.2 40

## Step 1<br />The problem involves the photoelectric effect, where a photon with sufficient energy can knock an electron out of a hydrogen atom. The energy of the photon is given as 13.6 eV.<br /><br />## Step 2<br />The kinetic energy of the ejected electron is determined by the energy of the photon. In this case, the photon's energy is exactly sufficient to remove the electron from the hydrogen atom.<br /><br />## Step 3<br />According to the photoelectric effect, the kinetic energy of the ejected electron is equal to the energy of the photon. Therefore, the kinetic energy of the ejected electron is also 13.6 eV.