this concept is even used to propel a kind without even having to leave my bed Radiation pressure can be Viewed as a consequence ofthe conservation of momentum ajven the momentum анльлед о electromagn

this concept is even used to propel a kind
without even having to leave my bed
Radiation pressure can be Viewed as a consequence ofthe conservation of momentum
ajven the momentum анльлед о electromagnetic aciation. That momentum can be equal
wel caleuates onthe bass of electromagnetic theory ог trom the combined momenta of
stream of photons, ging identical results as's shown below
‘Main arte: Poynting vector
Aecorcng to Manuel's theory of electromagnetism, an electromagnetic wave caries
‘momentum, which wil be transferred to an opaque surface it tikes.
‘Te energy их (radiance) of a plane wave is calculated using the Poynting vector
S = E x H, whose magnitude we denote by S.Sdvided by the speed of ight the
density ofthe near momentum per unt area (pressure) of the elecromagnetic fl. So,
dimensionally, the Poynting vector is Зонт of dag work wrich is the speed of
light, сем, тез pressure, AFlarea, That pressure 8 experienced as radiation pressure
where P is pressure (usually in Pascais), I, is the incident iradiance (usually in Wim?) and
C's the speed of ght in vacuum. Here, | = 3:34 NIGW.
ithe surface fs planar at an angle tothe Incident wave, the intensity across the surface
wil be geometrically reduced bythe cosine of that angle an the component ofthe radiation
force against the surface wil also be reduced by the cosine ога, resutng ina pressure:
“The momentum from the incident wave is in the same direction o that wave. But only the
component of hat momentum normal othe surface contibutes to the pressure onthe
surface, as gven above. The component of that force tangent to the surface s nt called
Radiation pressure from reflection | eat)
‘Te above treatment for an incident wave accounts forthe radiation pressure experienced
by a black (totally absorbing) body. the wave is specuary reflected, then the reco due to
the retlected wave wil further contibut tothe radiation pressure. n the case ofa perfect
reflector, this pressure wil be identical to the pressure caused by the incident wave:
Pact = Рода + Раши = 2
For a parialy reflective surface, the second term must be mulipied by the reflectivity (also
known as refection coefficient of intensity), во tha the increase is less than doubve. Рога
ee iGo the sayasfieRective bacalleavetiarcked
eae - ght transfers twice the momentum
* of absorbed light
so if | had а strong enough laser