Answer:

Explanation:
As we know that when electron moved in electric field then work done by electric field must be equal to the change in kinetic energy of the electron
So here we have to find the work done by electric field on moving electron
So we have



now the distance moved by the electron is given as

so we have



now we have to convert it into keV units
so we have


Answer:
when the ground is very hot and the air is cool.
Explanation:
The hot earth warms a layer of air right above the ground. Light is refracted as it passes through the cool air and onto the hot air sheet (bent). A coating of very warm air near the earth bends the light from the sky almost into a U-shaped bend.
The circuit is no longer closed.
I need to force in order to answer. What is it
Answer:
Frequency, f = 1 unit
Explanation:
It is given that,
Period of the wave, T = 1 unit
We need to find the frequency of the wave. There exist an inverse relationship between period and the frequency of the wave. It is given by :

Or


f = 1 unit
So, the frequency of the wave is 1 unit. Hence, this is the required solution.