[0:00]Hello everyone. So, aaj ka hamara topic hai application of total internal reflection aur aaj hum total reflecting glass prism ke bare mein padhenge. Toh chaliye lecture start karte hain. So basically glass prism kya hota hai? Yeh ek right angled isosceles prism hota hai. Right angled isosceles prism kya hota hai ki isme iska ek angle jo hai right angled hota hai, that is 90 degree aur jo baaki ke do angles hote hain woh isosceles hote hain. Isosceles ka matlab equal or similar, theek hai. Agar ek angle 90 degree hai toh baaki ke do angles kitne honge? 45 degree, 45 degree ke theek hai. 45 + 45, 90, 90 + 90, 180 degree. So sum of angles of triangle kitna ho gaya? 180 degree. Toh yeh hum use kab karte hain? Iska use kya hai ki jab humein apni image ko 90 degree ya 180 degree angle pe rotate karna hota hai toh hum glass prisms ka use karte hain. Ja aap keh lo ki jab humein erect image chahiye hoti hai toh hum kya karte hain? Glass prisms ka use karte hain. Aur yeh use kahan pe hote hain? Yeh cameras mein use hote hain, theek hai. Cameras mein jab humein image ko 90 degree or 180 degree pe rotate karna hai toh cameras mein glass prisms use hote hain. Usi tarah binoculars mein. Binoculars yani ke doorbin, theek hai. Doorbin mein bhi jab image ko rotate wagaira karna hota hai toh glass prisms ka hai use kiya jata hai. Usi tarah periscopes mein. Periscopes kya hai basically? Yeh ek submarine device hai jo obstacles ko detect karne ke liye use ki jati hai. Toh basically iska kaam kya hai glass prisms ka? Yeh humari light rays ko 90 degree or 180 degree angles pe rotate kar deta hai. Toh yahan pe ek aur main question jo arise hota hai woh hai ki hum yahan pe glass prisms hi kyun use karte hain? Hum yahan pe ek plane mirror kyun nahi use kar sakte? Agar hum plane mirror ko 45 degree angle pe rakh ke jo hai image obtain karein toh uska reason kya hai? Ki uska answer hai total internal reflection. Toh dekhiye kya hota hai bache plain mirror mein total internal reflection nahi hoti hai. Theek hai. Jaise plain mirror mein maine last lectures mein bhi bataya tha ki jab ispe light ray incident karti hai toh in kya hota hai ki jo aapki reflected light ray hoti hai woh 100% nahi hoti hai, theek hai.
[2:05]Isme jo hota hai energy losses hote hain. Kuch light ray jo hai woh refract kar jayegi, kuch is plain mirror mein absorb ho jayegi. Jo aapki reflected light ray hai woh total reflected nahi hoti hai. Theek hai. Usme 99% ya 98% jo hai reflect karti hai baaki 1-2% usme energy loss ho jata hai. Toh jo is case mein agar plain mirror se aap image obtain karoge toh uski quality itni acchi nahi hogi. But jabki glass prisms mein kya hota hai? Total internal reflection. Toh isme kya hota hai jo aapki reflected light ray hoti hai woh 100% hoti hai. Jisse image ki jo quality hai woh degrade nahi hoti hai. Toh isme aapko image quality jo hai woh same milti hai, object se compare kare toh. Jab ki plain mirror mein kya hota hai? Image quality degrade kar jati hai because ki wahan pe total internal reflection nahi hoti hai. So total internal reflection jo hai woh answer hai ki why we use glass prisms, theek hai. Toh aage dekhiye ki agar humein apni image ko 90 degree pe rotate karna hai toh kaise glass prism use karenge? So bache yeh hai hamara ek glass prism jiska ek angle 90 degree hai aur baaki ke do 45 degree theek hai. Aur isko yahan ek object hai AB, theek hai. Aur is object se jo hai do light rays jo hain jo hai is interface pe jo hai strike kar rahi hain. Aur humein dikh raha hai ki yahan pe kis angle pe incident kar rahi hain? 90 degree angle pe aur agar woh 90 degree angle pe incident karti hai toh without any deviation woh straight path follow karti hai. Toh yeh bina deviation ke straight path follow karti hui is interface pe strike ki. Ab dekho bache yeh angle kitna hai aapka 90 degree, theek hai. Yeh angle kitna hua 45 degree aur yeh kis yahan hum normal draw karenge toh yeh angle bhi kitna hoga? 45 degree. Main repeat kar rahi hoon, yeh 45 degree angle, theek hai. Yeh kitna tha aapka 90 degree, theek hai. Aur yeh kitna hua 45 degree. Agar yeh 45 degree hai toh yeh bhi kya hoga? 45 degree angle. Toh yeh light ray is interface pe kitne angle pe incident ki? 45 degree. Theek hai. Same isi pe bhi yahan pe bhi hum ek normal draw karenge. Yeh aapka angle 90 degree hai, yeh kitna tha 45 degree, agar yeh 45 degree hai toh yeh bhi kitna hua aapka 45 degree angle. Aur humein critical angle pata hai glass ka kitna hota hai? 42 degree. Ab aapka angle of incidence kitna hai? 45 degree, which is greater than critical angle. Aur ab yahan pe kya hogi? Total internal reflection. So yeh light ray kya karegi? Is medium mein iski kya ho jayegi? Total internal reflection. Aur yeh after reflection jo hai is interface pe strike ki. Ab dekho yeh is interface pe kitne angle pe incident kar rahi hai? Yeh kar rahi hai 90 degree angle pe. Hain na? Dekh ke pata lag raha hai. Toh again humein pata hai ki jab koi light ray 90 degree pe incident karti hai, then without any deviation woh apna straight path follow karti hai, theek hai. Toh yeh bhi straight path follow karti hui medium se bahar aa gayi, theek hai. Toh yahan pe aapki jo hai image form hogi. A' and B'. Toh ab aap dekh sakte ho ki jo aapki image hai woh kya kar ke hai? Object hai 90 degree angle pe rotate kar gaya. Yeh aapki image, theek hai. Object tha aise aur image form hui aise. Theek hai. AB aur yeh ho gaya this was your object AB aur image form hui A' B'. Ab aage dekhte hain ki agar humein apni image ko 180 degree pe rotate karna hai toh kaise karenge? Again hum wahi right angled isosceles prism hi use karenge jiska ek angle 90 degree hai aur baaki ke do angle kya hai isosceles, that is equal, hain na? Toh ab dekhiye same yahan pe ek object pada hai A B. Is object se light ray jo hai woh kya karegi? Is interface pe strike karegi, theek hai. Dekh ke pata lag raha hai kis angle pe incident ki is medium is interface mein? 90 degree pe aur without any deviation woh kya karegi? Straight path follow karegi. Yeh straight path follow karti hui is interface pe strike ki, theek hai. Again same yahan pe hum normal draw karenge. Theek hai. Yeh do normals draw kiye, theek hai. Yeh kya hai? 45 degree angle. Yeh kitna tha aapka 90 degree. Yeh kitna hua? 45 degree aur yeh bhi kitna ho gaya? 45 degree. Similarly yeh wali triangle mein dekhiye, yeh 45 degree, 90 degree, yeh 45 degree hai toh yeh bhi kitna hua? 45 degree. Critical angle kitna hai glass ka? 42 degree. Aur aapka angle of incidence kitna hai? 45 degree, greater than critical angle. Then yahan pe again kya hogi? Total internal reflection. Toh yeh dekhiye yahan pe yeh light ray kya kar jayegi? Yahan pe is interface pe strike karegi. Theek hai. Ab dekhiye is medium pe kis angle pe incident ki? 90 degree angle pe, theek hai. Yeh ho gaya aapka 90 degree angle, then agar woh 90 degree pe incident karti hai without any deviation woh kya karti hai straight path follow karti hui medium se bahar aa jati hai. Toh yeh straight path follow karti hui medium se bahar aa gayi.
[7:16]Toh yeh thi aapki B' aur yeh hai aapki A'. Toh aap dekh sakte ho ki jo aapki image hai woh aise thi, theek hai. This was your object aur image kya ban gayi? 180 degree pe, theek hai na.
[7:33]180 degree shift aa gaya AB aur yeh ban gayi aapke pass B' A'. Aur yeh maine ek pehle bata diya ki why we don't use plane mirror, glass prism hi kyun use karte hain? Toh uska answer tha total internal reflection.
[7:50]Ki jo isme aapko image milegi uski jo quality hai woh degrade nahi hogi, theek hai. Acchi quality ki jo hai image jo hai form hoti hai. So I hope aapko yeh lecture clear ho gaya hoga. Thank you so much for watching.
