Answer:Earth-orbiting astronauts are weightless for the same reasons that riders of a free-falling amusement park ride or a free-falling elevator are weightless. They are weightless because there is no external contact force pushing or pulling upon their body. In each case, gravity is the only force acting upon their body.
Explanation:
The energy required by the excitation of the line is:
ΔE = hν = hc / λ
where:
ΔE = energy difference
h = Planck constant
ν = line frequency
c = speed of light
λ = line wavelength
The energy difference must be supplied by the electron, supposing it transfers all its kinetic energy to excite the line:
Therefore,
And solving for v we get:
Plugging in numbers (after trasforing into the correct SI units of measurement):
=9.4 · 10⁵ m/s
Hence, the electron must have a speed of
9.4 · 10<span>
⁵ m/s in order to excite the <span>492nm</span> line.</span>
the speed of light is the right answer