Ultraviolet light with a wavelength shorter than visible light and a higher radiant energy than visible light.
The shorter the wavelength, the higher the frequency and energy.
Theories have both an explanatory an a predictive function. True
B. Fusion requires very high pressure and temperature.
Explanation:
Nuclear fusion is the combination of atomic nuclei into larger ones with the release of a large amount of energy.
Nuclear fission is the decay process in which a heavy nuclide is bombarded with with neutrons.
- Both processes release a huge amount of energy.
- But fusion produces far more energy.
- The reason why nuclear fusion is not in use is because of the high pressure and temperature needed start it.
- The activation energy is high and the energy barrier is very great.
- Only the core of the sun naturally favors fusion
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Answer:
<em>d. The sail should be reflective because in this case the momentum transferred to the sail per unit area per unit time is larger than for absorbing sail, therefore the radiation pressure is larger for the reflective sail.</em>
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Explanation:
Let us take the momentum of a photon unit as u
we know that the rate of change of momentum is proportional to the force exerted.
For a absorbing surface, the photon is absorbed, therefore the final momentum is zero. From this we can say that
F = (u - 0)/t = u/t
for a unit time, the force is proportional to the momentum of the wave due to its energy density. Therefore,
F = u
For a reflecting surface, the momentum of the wave strikes the sail and changes direction. Since we know that the speed of light does not change, then the force is proportional to
F = (u - (-u))/t = 2u/t
just as the we did above, it becomes
F = 2u.
From this we can see that the force for a reflective sail is twice of that for an absorbing sail, and we know that the pressure is proportional to the force for a given area. From these, we conclude that <em>the sail should be reflective because in this case the momentum transferred to the sail per unit area per unit time is larger than for absorbing sail, therefore the radiation pressure is larger for the reflective sail.</em>
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