(a) The force exerted by the electric field on the electron is given by the product between the electron charge q and the intensity of the electric field E:

Under the action of this force, the electron moves by:

And the work done by the electric field on the electron is equal to the product between the magnitude of the force and the displacement of the electron. The sign has to be taken as positive, because the direction of the force is the same as the displacement of the electron, so:

(b) The electron is initially at rest and it starts to move under the action of the electric field. This means that as it moves, it acquires kinetic energy and it loses potential energy. The change in potential energy is the opposite of the work done by the electric field:

Where Uf and Ui are the final and initial potential energy of the electron.
(c) For the conservation of energy, the sum of the kinetic energy and potential energy of the electron at the beginning of the motion and at the end must be equal:

(1)
where Ki and Kf are the initial and final kinetic energies.
The electron is initially at rest, so Ki =0, and we can rewrite (1) as

and by using the mass of the electron me, we can find the value of the final velocity of the electron:
Very high melting<span> points - Substances with giant covalent structures have very high</span>melting<span> points, because a lot of strong covalent bonds must be broken. Graphite, for example, has a </span>melting point<span> of more than 3,600ºC. Variable conductivity - Diamond does not conduct electricity.</span>
Answer:
For 6 its D
For 7 its A
For 8 its C
For 9 I think its B but Im not sure
Answer: Letter X in the diagram represent the angle of incidence
Explanation: One of the properties of wave is reflection. But before reflection can occur, there must have been a directed motion of wave particle towards a plane surface. The angle of incidence is the angle between the direction of motion of the wave particle ( for example; light) and the normal to the plane surface.