CLASS 10 SCIENCE - CHAPTER 9 NOTES
LIGHT - REFLECTION & REFRACTION
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PAGE 1: INTRODUCTION & LAWS OF REFLECTION
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[1.1] LIGHT (Prakash) KYA HAI?
* Definition: Light energy ka ek roop (form) hai jo humein hamare aas-pass ki
cheezon ko dekhne mein madad karta hai.
* Properties of Light:
1. Light hamesha ek seedhi rekha (Straight line) mein travel karti hai. Is
property ko 'Rectilinear propagation of light' kehte hain.
2. Light ek electromagnetic wave hai, isliye ise travel karne ke liye kisi
medium (jaise hawa ya pani) ki zaroorat nahi hoti. Yeh Vacuum (shunya)
mein bhi chal sakti hai.
3. Speed of Light: Vacuum/Air mein light ki speed sabse tez hoti hai
-> c = 3 x 10^8 m/s (3 lakh kilometer per second).
[1.2] REFLECTION OF LIGHT (Prakash ka Paravartan)
* Definition: Jab light ki ray kisi polished surface (jaise mirror) se takrakar
wapas usi medium mein laut aati hai, toh is bounce back hone ki process ko
Reflection kehte hain.
* Important Terms:
1. Incident Ray: Jo light ray surface par aakar girti hai.
2. Reflected Ray: Jo ray takrane ke baad wapas lautati hai.
3. Normal: Point of incidence par khेंची gayi ek perpendicular (90 degree) line.
4. Angle of Incidence (∠i): Incident ray aur Normal ke beech ka angle.
5. Angle of Reflection (∠r): Reflected ray aur Normal ke beech ka angle.
[1.3] LAWS OF REFLECTION (Paravartan ke Niyam)
1. First Law: Angle of incidence hamesha angle of reflection ke barabar hota hai (∠i = ∠r).
2. Second Law: Incident ray, Reflected ray aur Normal, ye teeno ek hi plane
(satah) par hote hain.
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PAGE 2: SPHERICAL MIRRORS (Goliya Darpan)
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[2.1] TYPES OF SPHERICAL MIRRORS
Wo mirror jinka reflecting surface curved (golaakaar) hota hai. Yeh do tarah ke hote hain:
1. Concave Mirror (Avatal Darpan): Iska reflecting surface andar ki taraf curve
hota hai (curved inwards). Yeh light ko ek jagah ik इकट्ठा karta hai, isliye
ise 'Converging Mirror' bhi kehte hain.
, 2. Convex Mirror (Uttal Darpan): Iska reflecting surface bahar ki taraf ubhra
hua hota hai (curved outwards). Yeh light ko phelata hai, isliye ise
'Diverging Mirror' kehte hain.
[2.2] IMPORTANT DEFINITIONS (Zaroori Paribhashayein)
* Pole (P): Spherical mirror ke reflecting surface ka center point.
* Center of Curvature (C): Mirror jis khokhle gole (hollow sphere) ka hissa hai,
uska center point.
* Radius of Curvature (R): P aur C ke beech ki doori.
* Principal Axis: Pole (P) aur Center of Curvature (C) se guzarne waali seedhi line.
* Principal Focus (F): Principal axis ke parallel aane waali rays takrane ke
baad jis point par milti hain (ya milti hui lagti hain).
* Focal Length (f): Pole (P) aur Focus (F) ke beech ki doori.
* Relation Formula: Radius hamesha focal length ki dugni hoti hai -> R = 2f (ya f = R/2).
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PAGE 3: IMAGE FORMATION BY CONCAVE & CONVEX MIRRORS
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[3.1] IMAGE FORMATION BY CONCAVE MIRROR
Concave mirror mein object (wastu) ki jagah ke hissab se 6 alag cases bante hain:
1. Object at Infinity: Image 'F' par banegi (Highly diminished, Real & Inverted).
2. Object Beyond C: Image 'C' aur 'F' ke beech banegi (Diminished, Real & Inverted).
3. Object at C: Image 'C' par hi banegi (Same size, Real & Inverted). [Most Imp]
4. Object Between C and F: Image 'C' se peeche banegi (Enlarged, Real & Inverted).
5. Object at F: Image Infinity par banegi (Highly enlarged, Real & Inverted).
6. Object Between P and F: Image mirror ke PEECHE banegi (Enlarged, Virtual & Erect).
[Only Virtual Case]
[3.2] IMAGE FORMATION BY CONVEX MIRROR
Convex mirror hamesha **Virtual, Erect (seedhi) aur Diminished (chhoti)** image hi banata
hai, chahe object kahin bhi rakha ho.
[3.3] USES OF MIRRORS (Darpan ke Upayog)
* Concave Mirror ke uses: Torches, Search-lights, Shaving mirrors aur dentists
ke zariye daant ka bada dekhne ke liye. Solar furnaces mein sunlight ko focus
karne ke liye.
* Convex Mirror ke uses: Vehicles (gaadiyon) ke Rear-view mirror ke roop mein,
kyunki yeh hamesha seedhi image banata hai aur iska field of view (dekhne ka area)
bohot bada hota hai.
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PAGE 4: SIGN CONVENTION & MIRROR FORMULA
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[4.1] NEW CARTESIAN SIGN CONVENTION (Chinha Paripati)
Numericals solve karne ke liye plus (+) aur minus (-) sign lagane ke niyam:
LIGHT - REFLECTION & REFRACTION
======================================================================
==========
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PAGE 1: INTRODUCTION & LAWS OF REFLECTION
--------------------------------------------------------------------------------
[1.1] LIGHT (Prakash) KYA HAI?
* Definition: Light energy ka ek roop (form) hai jo humein hamare aas-pass ki
cheezon ko dekhne mein madad karta hai.
* Properties of Light:
1. Light hamesha ek seedhi rekha (Straight line) mein travel karti hai. Is
property ko 'Rectilinear propagation of light' kehte hain.
2. Light ek electromagnetic wave hai, isliye ise travel karne ke liye kisi
medium (jaise hawa ya pani) ki zaroorat nahi hoti. Yeh Vacuum (shunya)
mein bhi chal sakti hai.
3. Speed of Light: Vacuum/Air mein light ki speed sabse tez hoti hai
-> c = 3 x 10^8 m/s (3 lakh kilometer per second).
[1.2] REFLECTION OF LIGHT (Prakash ka Paravartan)
* Definition: Jab light ki ray kisi polished surface (jaise mirror) se takrakar
wapas usi medium mein laut aati hai, toh is bounce back hone ki process ko
Reflection kehte hain.
* Important Terms:
1. Incident Ray: Jo light ray surface par aakar girti hai.
2. Reflected Ray: Jo ray takrane ke baad wapas lautati hai.
3. Normal: Point of incidence par khेंची gayi ek perpendicular (90 degree) line.
4. Angle of Incidence (∠i): Incident ray aur Normal ke beech ka angle.
5. Angle of Reflection (∠r): Reflected ray aur Normal ke beech ka angle.
[1.3] LAWS OF REFLECTION (Paravartan ke Niyam)
1. First Law: Angle of incidence hamesha angle of reflection ke barabar hota hai (∠i = ∠r).
2. Second Law: Incident ray, Reflected ray aur Normal, ye teeno ek hi plane
(satah) par hote hain.
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PAGE 2: SPHERICAL MIRRORS (Goliya Darpan)
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[2.1] TYPES OF SPHERICAL MIRRORS
Wo mirror jinka reflecting surface curved (golaakaar) hota hai. Yeh do tarah ke hote hain:
1. Concave Mirror (Avatal Darpan): Iska reflecting surface andar ki taraf curve
hota hai (curved inwards). Yeh light ko ek jagah ik इकट्ठा karta hai, isliye
ise 'Converging Mirror' bhi kehte hain.
, 2. Convex Mirror (Uttal Darpan): Iska reflecting surface bahar ki taraf ubhra
hua hota hai (curved outwards). Yeh light ko phelata hai, isliye ise
'Diverging Mirror' kehte hain.
[2.2] IMPORTANT DEFINITIONS (Zaroori Paribhashayein)
* Pole (P): Spherical mirror ke reflecting surface ka center point.
* Center of Curvature (C): Mirror jis khokhle gole (hollow sphere) ka hissa hai,
uska center point.
* Radius of Curvature (R): P aur C ke beech ki doori.
* Principal Axis: Pole (P) aur Center of Curvature (C) se guzarne waali seedhi line.
* Principal Focus (F): Principal axis ke parallel aane waali rays takrane ke
baad jis point par milti hain (ya milti hui lagti hain).
* Focal Length (f): Pole (P) aur Focus (F) ke beech ki doori.
* Relation Formula: Radius hamesha focal length ki dugni hoti hai -> R = 2f (ya f = R/2).
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PAGE 3: IMAGE FORMATION BY CONCAVE & CONVEX MIRRORS
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[3.1] IMAGE FORMATION BY CONCAVE MIRROR
Concave mirror mein object (wastu) ki jagah ke hissab se 6 alag cases bante hain:
1. Object at Infinity: Image 'F' par banegi (Highly diminished, Real & Inverted).
2. Object Beyond C: Image 'C' aur 'F' ke beech banegi (Diminished, Real & Inverted).
3. Object at C: Image 'C' par hi banegi (Same size, Real & Inverted). [Most Imp]
4. Object Between C and F: Image 'C' se peeche banegi (Enlarged, Real & Inverted).
5. Object at F: Image Infinity par banegi (Highly enlarged, Real & Inverted).
6. Object Between P and F: Image mirror ke PEECHE banegi (Enlarged, Virtual & Erect).
[Only Virtual Case]
[3.2] IMAGE FORMATION BY CONVEX MIRROR
Convex mirror hamesha **Virtual, Erect (seedhi) aur Diminished (chhoti)** image hi banata
hai, chahe object kahin bhi rakha ho.
[3.3] USES OF MIRRORS (Darpan ke Upayog)
* Concave Mirror ke uses: Torches, Search-lights, Shaving mirrors aur dentists
ke zariye daant ka bada dekhne ke liye. Solar furnaces mein sunlight ko focus
karne ke liye.
* Convex Mirror ke uses: Vehicles (gaadiyon) ke Rear-view mirror ke roop mein,
kyunki yeh hamesha seedhi image banata hai aur iska field of view (dekhne ka area)
bohot bada hota hai.
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PAGE 4: SIGN CONVENTION & MIRROR FORMULA
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[4.1] NEW CARTESIAN SIGN CONVENTION (Chinha Paripati)
Numericals solve karne ke liye plus (+) aur minus (-) sign lagane ke niyam:
