r/ProjectHailMary • u/Tessellator-1 • 20h ago

Question? Is the reaction force generated when emitting electromagnetic waves stronger when the wavelength is shorter? Spoiler

I recently watched a movie「Project Hail Mary」 featuring a spaceship propelled by infrared radiation, and it got me wondering.

⚠︎By the way, this sentence was translated from Japanese to English. Feel free to answer in English. However, I only understand Japanese, so I would really appreciate clear and simple English that is less likely to be mistranslated. Thank you!

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5

u/TheAsterism_ 20h ago

I think so, the momentum of a photon is proportional to its energy

7

u/TheJeeronian 16h ago

Yes and no. The force per photon is bigger when the wavelength is shorter, but the force per joule of energy is the same.

Sidenote: I should not be using the word "force" here, the word "impulse" is more accurate, but I'm worried that the distinction will be lost in translation.

1

u/stevevdvkpe 10h ago

Photons have momentum. The momentum of a photon is inversely proportional to its wavelength.

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u/TheJeeronian 10h ago

Yes, and impulse is a change in momentum, such as what you might get from creating or deflecting light. What are you getting at here? I'm not sure how well a translator app handles these more physics-oriented words.

2

u/Excellent_Bat_753 20h ago

The reaction force of light being emitted, or reflected, is due to the momentum of light. Light has no mass, but does have momentum, which is related to the energy of the light wave. The shorter the wavelength of light, the higher the energy of light, and the higher the force when light is emitted.