Hum Cheezein Dekhte Kaise Hain? 👁️
Ek andhere kamre mein aap kuch nahi dekh sakte — chaahe aankhein kitni bhi achhi hon. Kyun? Kyunki dekhne ke liye roshni ka aankh tak pahunchna zaroori hai.
Sooraj ya bulb roshni khud banate hain — inhe luminous kehte hain. Par kursi, kitaab, aapka chehra — ye roshni banate nahi. Ye sirf us par padi roshni ko wapas laut'ate hain. Isi laut'ne ko reflection (paraavartan) kehte hain.
📌 Aap kitaab isliye dekh paate hain kyunki bulb ki roshni kitaab par padti hai, wahan se reflected hokar aapki aankh tak pahunchti hai. Bina reflection ke duniya ki zyadatar cheezein dikhti hi nahi.
Roshni hamesha seedhi rekha mein safar karti hai — isi ko
rectilinear propagation kehte hain. Isi wajah se parchhai (shadow) banti hai, aur
isi wajah se aap deewar ke peeche nahi dekh sakte.
Aur roshni ki raftaar? Vacuum mein 3 × 108 metre/second — yani ek
second mein prithvi ke saat chakkar! Ye prakriti ki sabse tez raftaar hai; isse tez kuch bhi nahi
chal sakta.
📜 Reflection Ke Do Niyam
Poora chapter — mirror (darpan), lens, sab — in do chhote niyamon par khada hai. Inhe achhe se samajh lo.
📌 Niyam 1: Angle of incidence (aapaat kon) = angle of reflection, yani ∠i = ∠r
📌 Niyam 2: Incident ray, normal aur reflected ray — teeno
ek hi tal (plane) mein hote hain.
⚠️ Sabse aam galti: kon hamesha NORMAL se naapa jaata hai, mirror
ki satah se nahi! Agar roshni mirror par 30° ki satah-wali dhaal se aaye, toh i = 90° − 30° =
60° hoga.
Q: Ek ray mirror par perpendicular girti hai. i aur r
kya honge?
Hal: Perpendicular girne ka matlab ray normal ke saath-saath hai.
Toh i = 0°, aur niyam se r = 0°.
Yani ray usi raaste se seedhi wapas laut jaayegi. Isiliye seedha mirror mein
dekhne par aapko apna hi chehra dikhta hai.
Kyunki reflection do tarah ka hota hai:
🔹 Regular reflection — chikni satah (mirror, shaant paani). Saari parallel rays
parallel hi lautti hain → saaf image banta hai.
🔹 Diffused reflection — khurdari satah (deewar, kaagaz, kapda). Har chhote hisse
ka normal alag disha mein hai, isliye rays bikhar jaati hain → image nahi banta,
par cheez har taraf se dikhti hai.
Zaroori baat: diffused reflection mein bhi dono niyam poori tarah lagte
hain! Har ek ray ke liye i = r hai. Bikhraav satah ki khurdari se aata hai, niyam
todne se nahi.
🪞 Plane Mirror Ka Image
Ab sochte hain: aap mirror ke saamne khade hain. Aapka image kaisa hai?
📌 Plane mirror ke image ke 5 gun:
1️⃣ Virtual — parde (screen) par nahi pakad sakte
2️⃣ Erect (seedha) — kabhi ulta nahi
3️⃣ Utna hi bada — size bilkul same (m = +1)
4️⃣ Utni hi doori par — mirror ke peeche, utni hi doori
5️⃣ Laterally inverted — baayan haath daayan dikhta hai
🔹 Real image — jab reflected/refracted rays sach mein milti hain.
Ise aap parde par pakad sakte hain. Cinema hall ka parda, camera ka sensor — sab
real image.
🔹 Virtual image — jab rays sach mein milti nahi, sirf
milti hui lagti hain (unhe peeche badhaana padta hai). Parde par
bilkul nahi pakad sakte. Mirror mein aapka chehra — virtual.
Yaad rakhne ka tareeka: mirror ke peeche parda rakh do — kuch nahi dikhega. Kyunki
wahan roshni pahunch hi nahi rahi!
↔️ Lateral Inversion — Ambulance Wali Baat
Aapne dekha hoga ki ambulance ke aage
AMBULANCE
is tarah ulta likha hota hai. Kyun?
Kyunki aage chal rahe driver ise apne rear-view mirror mein dekhta hai. Mirror
lateral inversion kar deta hai — toh ulta likha hua shabd mirror mein
seedha "AMBULANCE" dikhta hai! Driver turant samajh jaata hai aur raasta de deta
hai.
Ye ek chhoti si physics ki samajh hai jo roz zindagi bachati hai.
⚠️ Ek gehri baat: mirror asal mein baayan-daayan
palat'ta nahi hai! Wo aage-peeche (front-back) palat'ta hai.
Soch kar dekho: mirror mein aapka sar upar hi hai (upar-neeche nahi palta), aur baayan haath bhi
wahin hai jahan tha. Jo palta hai wo hai aapke aage ki disha — image aapki taraf
munh karke khada hai. Isi ghumav ko hum "baayan-daayan palat gaya" samajh lete hain.
Isi wajah se agar aap let kar mirror mein dekhein, toh "lateral" inversion
upar-neeche jaisa lagne lagta hai!
Q: Ek 180 cm lambe aadmi ko apna poora shareer dekhne ke liye kam
se kam kitna lamba mirror chahiye?
Hal: Ye sunkar lagta hai 180 cm chahiye — par jawab hai
sirf 90 cm!
Kyun? Sar se aayi ray ko aankh tak pahunchne ke liye mirror ka jo bindu chahiye, wo
sar aur aankh ke beech ke bilkul aadhe par hai (kyunki i = r). Waise hi pair se
aayi ray ke liye bindu aankh aur pair ke aadhe par hai.
Toh zaroori lambai = aadmi ki lambai ÷ 2 = 180/2 = 90 cm.
Aur mazedaar baat: ye jawab is baat par nirbhar nahi karta ki aap
mirror se kitni door khade hain! Paas jao ya door — 90 cm ka mirror hi kaafi rahega.
Kerala ke Aranmula gaon mein sadiyon se ek khaas mirror banta hai —
"Aranmula Kannadi". Ye kaanch ka nahi, ek khaas
metal (dhaatu) ki alloy (metal alloy) ko ghis-ghis kar chamkaya jaata hai.
Iska faayda kya? Aam kaanch ke mirror mein roshni pehle kaanch se guzarti hai, phir peeche wali
chaandi ki parat se lautti hai — isse ek halka sa doosra image ban jaata hai. Metal
mirror mein roshni seedhe upari satah se lautti hai, isliye image
bilkul saaf hota hai — koi doosri parchhai nahi.
Ise front-surface mirror kehte hain, aur aaj bhi bade telescope aur vaigyanik
upkaran isi siddhaant par bante hain. Aranmula Kannadi ko GI tag mila hua hai.
🧠 Apne Aap Ko Test Karo
🧊 3D Optical Bench par asli rays ko mudte aur milte dekho!
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