PhysicsHiranyagarbha · Class 11-12
Photon ki energy aur fibre ka jaadu: optogenetics ki physics
Ek neeli photon aur ek laal photon, dono roshni hain. Phir protein ka gate sirf neeli par kyun khulta hai, aur roshni dimaag ke andar tak kaise pahunchti hai?
Socho pehle… phir dekho jawab
Photon ki energy E = hc/λ hai: chhoti wavelength, zyada energy. Aur roshni ko andar tak le jaane ka kaam total internal reflection (TIR) wali optical fibre karti hai.
Photon energy: E = hc/λ, ya eV mein E ≈ 1240/λ(nm). Neeli roshni (450 nm) ka photon lagbhag 2.8 eV ka, laal (700 nm) ka lagbhag 1.8 eV ka. Molecule wahi photon sokhte hain jinki energy unke andar ke badlaav se mel khaaye. Isliye channelrhodopsin-2 neeli roshni par khulta hai.
TIR: jab roshni zyada refractive index wale maadhyam se kam wale ki taraf jaati hai aur angle critical angle C se bada ho, toh poori roshni andar laut aati hai. sin C = n2/n1. Kaanch-hawa (n = 1.5) ke liye sin C = 1/1.5, yaani C ≈ 41.8°. Fibre ka core cladding se zyada index ka hota hai, isliye roshni core mein hi bandhi rehti hai.
Card ka timeline: 1990s mein alga Chlamydomonas ka sawaal, phir channelrhodopsin-1 aur -2; 2005 mein rat neurons par pehla bada result; 2007 mein fibre-optic cable se roshni bhej kar zinda chuhe ki moonchh hilaayi gayi.
Trade-off: chhoti wavelength wali neeli roshni tissue mein zyada bikharti (scatter) aur sokhi jaati hai, isliye gehraai tak nahi jaati. Isi liye fibre andar le jaani padti hai. Lambi wavelength gehri jaati hai, par har protein us par nahi khulta. Physics yahan design ki seema bhi batati hai.
Ghar pe try karo
Calculate karo: 470 nm, 550 nm aur 650 nm ke photon ki energy eV mein (E ≈ 1240/λ). Phir n1 = 1.50 (core) aur n2 = 1.48 (cladding) lekar critical angle nikaalo. Kya yeh kaanch-hawa wale 41.8° se bada hai ya chhota?
Wow!
Ek hi gene se bana protein ek saath light-sensor aur ion-gate hai. Physics ki ek photon se biology ka ek signal!
3 sawaal
- E ≈ 1240/λ(nm) se 450 nm photon ki energy lagbhag kitni?
Jawab dekho
2.8 eV. 1240/450 ≈ 2.76, yaani lagbhag 2.8 eV.
- Optical fibre mein roshni core mein kyun rehti hai?
Jawab dekho
Total internal reflection, kyunki core ka refractive index cladding se zyada hai. TIR ke liye roshni zyada index se kam index ki taraf jaani chahiye, isliye core ka index zyada rakha jaata hai.
- Neeli roshni tissue mein gehraai tak kyun nahi jaati?
Jawab dekho
Chhoti wavelength zyada scatter aur absorb hoti hai. Chhoti wavelength tissue mein zyada bikharti aur sokhi jaati hai, isliye fibre chahiye.
NCERT se jodo: NCERT Class 12 Physics — dual nature of radiation (photon energy) aur ray optics (total internal reflection, optical fibre)