Base in your questions that ask what cause the bright lines seen in the emission spectrum and i think the best answer to that is the H2 gas is used when protons was heated so the electron absorb all the photons and get exited and resulted by given of a light.
Answer:
a.
b.
c. 
Explanation:
Use Gravitational Force:

Use values given to have the results.
b.

Use m as the mass of the Moon. Using values of a. and m you have the answer.
c.

Use M mass of the planet. Use value of a and Mass of Planet.
The magnitude of the change in potential energy is equal to the kinetic energy,

or
Here, V is potential difference, q is charge, m is mass and v is velocity.
We can also write,

Given 
Substituting this value with mass of proton,
and charge of proton,
we get

Therefore, the speed of proton is
.
Explanation:
i wish I could help you but its not clear...