Radiation Pressure: Momentum Transfer, Comets, and Light Sails

All flashcards

Radiation pressure

Pressure exerted when electromagnetic radiation transfers momentum to a surface.

Absorption and reflection at normal incidence

An ideal absorber experiences $p=I/c$; an ideal reflector experiences $p=2I/c$.

Solar wind and comet tails

The solar wind shapes the ion tail; sunlight's radiation pressure pushes neutral dust.

Solar intensity at distance $r$

For solar power $P$, intensity is $I=P/(4\pi r^2)$.

Light-sail acceleration

For net force $F$ and spacecraft mass $m$, acceleration is $a=F/m$.

Quiz questions

1. For normally incident light of intensity $I$, what pressure does an ideal perfectly reflecting surface experience?Answer: $2I/c$
2. Which force primarily shapes the ion tail of a comet?Answer: Interactions between ions and the solar wind
3. If the Sun emits power $P$, what is the sunlight intensity at distance $r$, assuming uniform spreading in all directions?Answer: $I=P/(4\pi r^2)$
4. What equation gives the radiation force on a surface of area $A$ experiencing pressure $p$?Answer: $F=pA$
5. For a light sail receiving a net force $F$, how is the spacecraft's acceleration $a$ related to its total mass $m$?Answer: $a=F/m$