Energy and matter can neither be created or destroyed.
Explanation:
In the given situation two forces are working. These are:
1) Electric force (acting in the downward direction) = qE
2) weight (acting in the downward direction) = mg
Therefore, work done by all the forces = change in kinetic energy
Hence, 
It is known that the weight of electron is far less compared to electric force. Therefore, we can neglect the weight and the above equation will be as follows.
v = 
= 592999 m/s
Since, the electron is travelling downwards it means that it looses the potential energy.
Answer: The maximum possible speed v is √2( hν - Ф ) / m
Explanation: You could be referring to the provided explanation, despite the fact that the question isn't comprehensive. When a photon collides with the surface of any metal, it transmits all of its energy to the electron in the atom. The collision causes the electron to travel with a certain amount of kinetic energy. This is referred to as the photoelectric effect. The maximum kinetic energy is calculated using Einstein's equation for the photoelectric effect:
K.E. = hν - Ф
½ mv² = hν - Ф
Hence the maximum possible speed is:
v = √2( hν - Ф ) / m
For more information on the photoelectric effect refer to this link: brainly.com/question/25027428
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Yes it is true medium moves parallel to wave motion.
