Manav netra class 10 notes mein hum NCERT Science Chapter 10 ke teen bade topics cover karenge: (1) manav aankh — uski rachna aur drishti dosh, (2) prism se prakash ka apvartan aur varn-vikshepan (dispersion), (3) vatavaraniya apvartan aur prakash ka prakirnan (scattering). Board exam 2027 mein is chapter se 3–5 marks ke sawaal pakke aate hain — diagram-based aur reason-based dono. Notes simple bhasha mein, exam-point style mein de rahe hain.
Manav aankh lagbhag 2.3 cm diameter ka golakar ang hai. Prakash aankh mein aage se peechhe is kram mein jata hai:
Aankh ke mukhya bhag aur unke kaam
- Cornea — aankh ke aage ka pardarshi ubhaar; aankh mein pravesh karne wale prakash ka sabse zyada apvartan (refraction) yahin hota hai — lens mein nahi (yeh exam mein aksar poochha jata hai)
- Iris — cornea ke peechhe rangin maanspeshiyon ka pardaa; pupil ka aakaar control karke aankh mein jane wale prakash ko regulate karta hai
- Pupil — iris ke beech ka kaala chhed; andhere mein phailta hai, tez roshni mein sikudta hai
- Crystalline lens (netra lens) — pupil ke peechhe pardarshi ubhay-uttol (biconvex) lens; ciliary muscles iski vakrata (curvature) badalkar focus fine-tune karte hain
- Retina — aankh ke peechhe prakash-samvedi parda; is par ulta (inverted) vaastavik pratibimb banta hai
- Rods aur Cones — retina ki samvedi koshikayein; rods prakash ki tivrata (intensity) pehchante hain, cones rang pehchante hain
- Optic nerve — retina se vidyut sanket mastishk tak pahunchata hai; mastishk ulte pratibimb ko seedha samajhta hai
- Aqueous humour — cornea aur lens ke beech pani jaisa drav
- Vitreous humour — lens ke peechhe jelly jaisa drav; retina ko apni jagah par rakhta hai
- Blind spot — jahan optic nerve retina se judta hai; wahan samvedi koshikayein nahi hoti, isliye dikhai nahi deta
- Yellow spot (macula/fovea) — retina ka madhya bhag jahan cones sabse ghane hote hain; sabse tez rang-drishti yahin hoti hai
Samanjan kshamta (Power of Accommodation)
- Paribhasha: netra lens ki focal length badalne ki kshamta (vakrata badalkar), taaki nazdeek aur door dono vastuein retina par focus hon
- Nikattam bindu (near point) = 25 cm (samanya yuva vyakti)
- Door bindu (far point) = anant (infinity)
- 25 cm se nazdeek ki vastu dhundli dikhti hai — lens ki focal length ki ek nyuntam seema hoti hai
- Persistence of vision = 1/16 second — isi siddhant par chalchitra (motion pictures) kaam karte hain
2. Drishti Dosh (Defects of Vision)
Myopia (nikat-drishti dosh)
- Lakshan: nazdeek ki vastu saaf, door ki dhundli
- Kaaran: netra golak ka lamba ho jana ya netra lens ki atyadhik vakrata; door ki vastu ka pratibimb retina ke aage banta hai; door bindu nazdeek aa jata hai
- Sudhaar: avtal (concave/diverging) lens — uchit kshamta ka
Hypermetropia (door-drishti dosh)
- Lakshan: door ki vastu saaf, nazdeek ki dhundli
- Kaaran: netra golak ka chhota ho jana ya lens ki focal length ka zyada lamba hona; nazdeek ki vastu ka pratibimb retina ke peechhe banta hai; nikat bindu door hat jata hai
- Sudhaar: uttal (convex/converging) lens — uchit kshamta ka
Presbyopia (jara-door-drishtita)
- Kaaran: umr ke saath ciliary muscles kamzor aur lens kam lachila; samanjan kshamta ghatti hai; nikat bindu umr ke saath door hat-ta jata hai
- Sudhaar: bifocal lens (neeche nikat ke liye, upar door ke liye)
Cataract (motiyabind)
- Umr ke saath lens doodhiya/dhundla ho jata hai — aanshik ya poori drishti hani
- Shaly-chikitsa (surgery) se sudhaar sambhav hai
Exam tip: Myopia vs Hypermetropia ka antar — kaaran, lakshan aur sudhaar — table banakar yaad karein; 3 marks ka sawaal pakka.
3. Prism Se Prakash Ka Apvartan
- Kaanch ke prism mein do tribhujakar aadhar aur teen aayataakar parshv hote hain, jo ek kon par jhuke hote hain
- Prakash pehle satah par abhilamb ki taraf aur doosri satah par abhilamb se door mudta hai; antim nirgaman kiran aadhar (base) ki taraf jhukti hai
- Vichalan kon (angle of deviation, D): mool aapatan kiran aur antim nirgaman kiran ke beech ka kon
- Mahatvapurna NCERT bindu: prism se nikalne wali kiran aapatan kiran ke samantar NAHI hoti (aayataakar kaanch slab mein samantar hoti hai — yahi antar exam mein poochha jata hai)
4. Shwet Prakash Ka Varn-Vikshepan (Dispersion)
- Prism se guzarne par shwet prakash 7 rangon mein bat jata hai — kram: VIBGYOR (Violet, Indigo, Blue, Green, Yellow, Orange, Red)
- Baingani (violet) sabse zyada mudta hai, laal (red) sabse kam — alag-alag rangon ki tarangdairdhya (wavelength) alag hoti hai, isliye kaanch mein unki chaal alag hoti hai
- Spectrum: 7 rangon ki patti
- Indradhanush (rainbow): soorya ka prakash paani ki chhoti boondon par padta hai; har boond mein apvartan + varn-vikshepan + aantrik paravartan hota hai; indradhanush soorya ke vipreet disha mein, aam tor par baarish ke baad dikhta hai
5. Vatavaraniya Apvartan (Atmospheric Refraction)
- Taaron ka timtimana: vatavaran ki bhautik sthiti lagatar badalti rehti hai; door ke bindu-srot (taare) se aane wala prakash alag-alag matra mein mudta hai — isliye taare timtimate hain
- Grah nahi timtimate — ve vistaarit srot hain; utaar-chadhaav ausat ho jate hain
- Kshitij ke paas taare apni vaastavik sthiti se thode upar dikhte hain
- Agrim suryodaya / vilambit suryast: vatavaraniya apvartan ke kaaran soorya vaastavik suryodaya se lagbhag 2 minute pehle aur vaastavik suryast ke lagbhag 2 minute baad tak dikhta hai — din lagbhag 4 minute lamba ho jata hai
- Suryodaya/suryast ke samay soorya ka chapta dikhna — soorya ke upari aur neechle bhag se aane wali kirnein alag-alag matra mein mudti hain
6. Prakash Ka Prakirnan (Scattering of Light)
- Tyndall effect: colloidal kanon dwara prakash ka prakirnan — NCERT udaharan: dhuein bhare kamre mein chhote chhed se aati soorya-kiran ka patla prakash-punj; ghane jungle mein pedon ki chhatri se guzarta prakash (dhund ki chhoti boondein prakirnan karti hain)
- Neela aasmaan: bahut chhote kan mukhya roop se kam tarangdairdhya wale neele prakash ka prakirnan karte hain
- Suryodaya/suryast par laal soorya: prakash sabse lamba rasta tay karta hai; neela prakash bikhar jata hai, sirf lambi tarangdairdhya wala laal/narangi aankh tak pahunchta hai
- Khatre ke sanket laal: laal rang dhuein/kohre mein sabse kam bikhar ta hai, isliye door se dikhta hai
Exam Ke Liye Quick Revision
- Cornea mein sabse zyada apvartan hota hai — lens mein nahi
- Near point 25 cm, far point infinity, persistence of vision 1/16 second
- Myopia = concave lens, Hypermetropia = convex lens, Presbyopia = bifocal
- Prism mein nirgaman kiran aapatan kiran ke samantar NAHI hoti
- Violet sabse zyada, red sabse kam vichalit hota hai
- Taare timtimate hain (bindu srot), grah nahi (vistaarit srot)
- Suryodaya 2 minute pehle, suryast 2 minute baad — vatavaraniya apvartan
- Neela aasmaan aur laal soorya — prakirnan; khatre ka laal sanket — kam prakirnan
Aur study notes ke liye Students section dekhte rahein.