<span>Boiling water.The heat passes from the burner into the pot, heating the water at the bottom. Then, this hot water rises and cooler water moves down to replace it, causing a circular motion.</span>
Helium because it has 2/2 electrons already
(a) The electron kinetic energy is

which can be converted into Joule by keeping in mind that

So that we find

The kinetic energy of the electron is related to its momentum p by:

where m is the electron mass. Re-arranging the equation, we find

And now we can use De Broglie's relationship to find its wavelength:

where h is the Planck constant.
(b) By using the same procedure of part (a), we can convert the photon energy into Joules:

The energy of a photon is related to its frequency f by:

where h is the Planck constant. Re-arranging the equation, we find

And now we can use the relationship between frequency f, speed of light c and wavelength

of a photon, to find its wavelength:
Explanation:
Wave is defined as a disturbance or oscillation that travels through space-time, accompanied by a transfer of energy. Wave motion transfers energy from one point to another, often with no permanent displacement of the particles of the medium.
The velocity of wave is equal to the product of its wavelength and frequency (number of vibrations per second). Longitudinal waves like sound waves travel through a medium.
Therefore, a wave move from a layer of high velocity to that of a lower velocity the wavelength changes (that is, decreases) as it moves.