3.2.35 · D1Solar radiation pressure
Sunlight ek aisi nadi hai jo choti-choti momentum-carrying bullets — jise photons kehte hain — se bhari hai, aur bhale hi har ek photon unbelievably chhota ho, Sun itni badi tadaad mein fire karta hai ki woh milkar kisi bhi space object ko ek steady, halki si push dene lagte hain. Us push ko predict karne ke liye hume bas yeh karna hai: count karo kitni light-energy har second ek surface par girti hai, us energy ko momentum mein badlo, aur dekho ki light chipki ya uchhal gayi.
Is page par kuch bhi assume nahi kiya gaya . Isse pehle ki tum Solar radiation pressure padho — sorry, isse pehle ki tum parent topic Solar radiation pressure padho — usmein jo bhi letter, ratio, aur Greek symbol aata hai, woh sab yahan neeche se upar tak build kiya gaya hai. Top se bottom padho; har ek brick usse pehle waali par tikhi hai.
Definition Energy — symbolE Energy woh "capacity" hai jo kisi cheez mein change laaye — use heat kare, hilaye, ya roshan kare. Hum ise letter E joule (J light ke roop mein aati hai, aur yahi E
Definition Power, aur wattPower energy per second hai — yani energy kitni tezi se deliver hoti hai. Iska unit watt (W 1 W = 1 J/s
Hume E steady stream se matlab hai. "Per second" is poore topic mein baka hai. Force khud, jaise hum dekhenge, ek "per second" quantity hai.
Neeche ka figure dekho. Naranga bulb ek fixed power (60 W) emit karta hai. Clock ki har tick par, ek naaya identical 60-joule packet bahar nikalta hai — figure clearly batata hai ki "power = energy delivered every second." Woh per-second ki heartbeat yaad rakho: woh wahi beat hai jo baad mein intercepted light-energy ko ek steady force mein badal deti hai.
Definition Speed of light — symbolc c c ≈ 3 × 1 0 8 m/s c celeritas , Latin mein "swiftness" ke liye) physics mein universal hai. Yeh isliye aata hai kyunki light ka momentum us speed se juda hai jis par woh move karti hai — light ki push ko uski speed se alag nahi kar sakte.
hota hai, ek tasveer mein
Momentum hai "kisi cheez ko rokna kitna mushkil hai jab woh chal rahi ho." Ek chalti bowling ball mein bahut momentum hota hai (rokna mushkil); ek chalte ping-pong ball mein thoda. Jab koi chalti cheez tumse takraati hai aur ruk jaati hai, woh tumhe apna momentum de deti hai — woh handover ek push hai.
Definition Momentum — symbolp momentum p = m v m v kg⋅m/s
Neeche ka figure dekho. Is poore topic ke liye key idea bottom row hai: jab ek bullet wall se takraati hai aur chip jaati hai , wall ko bullet ka momentum p seedha wapas uchhalti hai , woh − p p − ( − p ) = 2 p do guna push. Woh "do guna" yaad rakho; yahi mirror-vs-black-paint ka fact hai jis par parent topic tikha hai.
Common mistake "Light mein mass nahi hai, tohp = m v = 0 Yeh sahi kyun lagta hai: tumne sirf p = m v m = 0 Fix yeh hai: p = m v slow-object ka rule hai. Light ek alag rule follow karti hai (agla section) jo use bina mass ke momentum deta hai. Momentum "hamesha mass times velocity" nahi hai — yeh ek conserved book-keeping quantity hai, aur light ke paas kuch hota hai. Dekho Photon momentum and relativity .
Light ek smooth continuous stream nahi hai — yeh chhote indivisible packets mein aati hai jise photons kehte hain. Ek machine gun ki tarah socho jo har second millions light-bullets fire karti hai. Har photon ek specific amount energy E E
Intuition Yeh ek formula sab kuch kyun unlock karta haiAgar tum jaante ho ki har second kisi surface par kitni light-energy girti hai, toh tum use 1/ c momentum gir raha hai — aur momentum-per-second ek force hai. Poora topic yahi hai: energy count karo, c
Definition Force — symbolF Force ek push ya pull hai. Newton ki insight: force woh momentum hai jo har second deliver hota hai . Agar koi stream har second momentum p p hai . Unit: newton (N 1 N = 1 kg⋅m/s 2
Definition Pressure — symbolP Pressure force ko area par spread karna hai: P = F / A pascal (Pa 1 Pa = 1 N/m 2
Topic pehle pressure ki baat kyun karta hai aur force ki baad mein? Kyunki sunlight per square metre aati hai — yeh naturally ek pressure hai. Apne actual spacecraft par force paane ke liye tum pressure ko uske area se multiply karte ho. Yahi logical order hai jo parent note follow karta hai.
Definition Acceleration aur mass — symbolsa m Mass m kg Acceleration a F = ma a = F / m force par nahi, acceleration par khatam hota hai — orbits a
Definition Luminosity — symbolL ⊙ L ⊙ total power hai jo Sun har direction mein radiate karta hai: L ⊙ ≈ 3.83 × 1 0 26 W ⊙
Definition Distance — symbolr r astronomical units (AU 1 AU ≈ 1.5 × 1 0 11 m
Intuition Wahi light door jaane par kamzor kyun padti hai — sphere pictureSun ki power sab directions mein equally stream hoti hai. Doori r r 4 π r 2 chaar guna ho jaata hai → light chaar guna patli ho jaati hai. Yeh "4 π r 2 1/ r 2
Ab chain ek saath jud jaati hai: S c pressure :
P rad = c S .
Definition Surface normal, aur angleθ Normal ek surface se seedha bahar nikla hua arrow hota hai, uske perpendicular — jaise ek pencil tabletop par balanced ho. Angle θ taraf ki direction ke beech measure kiya jaata hai. Agar surface Sun ki taraf seedha face kar rahi hai, θ = 0 θ = 9 0 ∘
Definition Reflectivity — symbolη η 0 1 η = 0 η = 1 ( 1 + η ) × 1 × 2
Common mistake "Edge-on se zyada tilt hua surface phir bhi sunlight pakad leti hai."Yeh sahi kyun lagta hai: tum koi bhi θ cos θ Fix yeh hai: θ > 9 0 ∘ doori face kar rahi hai — uska lit side shadow mein hai, toh koi sunlight nahi girti aur force zero hai, negative nahi. Mathematically cos θ clamp karo: max ( cos θ , 0 ) 0 ≤ θ ≤ 9 0 ∘
Ab har symbol defined hai. Dekho yeh sab ek expression mein kaise click karte hain, ek factor ek time.
Definition Area-to-mass ratio — symbolA / m A m A / m A / m A / m Solar sails versus ek heavy orbiter, aur Orbital perturbations mein ek perturbation ke roop mein uska role.
Har node ek symbol aur uska plain meaning batata hai, toh tum diagram ko seedha upar diye definitions se map kar sako.
Power = E per second, watts
Radiation pressure Prad = S over c
Intensity S = power per area
Sphere area 4 pi r squared
Force F = Prad times A times one plus eta times cos theta
Acceleration a = F over m
Area to mass ratio A over m
Ise ek nadi ki tarah padho: energy E c L ⊙ 4 π r 2 S c P rad cos θ F
Right side cover karo aur khud ko test karo. Agar koi bhi jawab surprising lage, toh parent note kholne se pehle woh section dobara padho.
Power kya hai, ek phrase mein, aur uska unit? Energy delivered per second; the watt (W = J/s
Energy ko kaun sa letter denote karta hai, aur uska unit? E J
c The speed of light, ≈ 3 × 1 0 8 m/s
Ordinary momentum formula aur uska unit? p = m v kg⋅m/s
Light-momentum rule aur kyun yeh p = m v p = E / c p = m v
Ek mirror ko black paint se do guna zyada push kyun milti hai? Ek bounced photon momentum reverse kar deta hai (p → − p p 2 p
Force ko "per second" idea se kaise state karein? Force = momentum delivered per second; unit newton (N
Pressure ki definition aur uska unit? Force per area, P = F / A Pa = N/m 2
Newton ka force, mass, acceleration ke beech link? F = ma a = F / m
L ⊙ Woh total power jo Sun sab directions mein radiate karta hai, ≈ 3.83 × 1 0 26 W
Light 1/ r 2 Fixed power 4 π r 2 r 2
Intensity S Power per area, S = L ⊙ / ( 4 π r 2 ) ≈ 1361 W/m 2
Angle θ Surface normal aur Sun ki direction ke beech.
θ > 9 0 ∘ Surface doori face karti hai, koi light nahi girti — cos θ 0
η η = 0 η = 1 Reflectivity; 0 1
Ek plate par poora simple force formula? F = ( S / c ) A ( 1 + η ) cos θ 0 ≤ θ ≤ 9 0 ∘
Orbits A / m SRP acceleration area-to-mass ke saath scale karta hai, toh light high-area craft ise strongly feel karte hain.
Solar radiation pressure — woh parent topic jise yeh foundations unlock karte hain.Photon momentum and relativity — p = E / c Inverse-square law — sphere area ke zariye intensity 1/ r 2 Solar sails — extreme high-A / m Orbital perturbations — jahan resulting acceleration matter karta hai. 
