Explanation:
Given that,
Wavelength of the light, 
Work function of sodium, 
The kinetic energy of the ejected electron in terms of work function is given by :

The formula of kinetic energy is given by :

Hence, this is the required solution.
When we swim we apply force and push the water backward with the help of our hands. In response, The water pushes us forward with an equal force. Thus, in order to move forward and swim, the swimmer lushes the water backward. Newton's 3rd law of motion
Explanation:
To find the resultant force subtract the magnitude of the smaller force from the magnitude of the larger force. The direction of the resultant force is in the same direction as the larger force