Answer:
A. Light can travel trough air and space.
Explanation:
A vacuum is space that has no air inside of it. Since light is able to go through 'nothing' and matter, your answer must be A.
Answer:
(c) 6.91x10^14 Hz
Explanation:
Find the level energy of n=2 and n=5, using the formula:

where 


To jump from n=2 to n=5 the electron absorbs a photon with energy equal to
, using the next formula to find specific wavelength
to that energy

Where
is the speed of light (
) and
is Planck's constant (
). Solve for
:

The frequency of this wavelength is calculated with this formula:


Answer:
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