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हार्मोनल परिवर्तन के कारण कम उम्र में लड़कियों में हो रहा शारीरिक परिवर्तन

हार्मोनल परिवर्तन के कारण कम उम्र में लड़कियों में हो रहा शारीरिक परिवर्तन प्रदुषण और जंक फूड घटा रहा मुश्किल भरे दिन की उम्र लड़कियों में समय से पहले हार्मोनल चेंज के मामले बढ़ रहे हैं। शारीरिक बदलाव के लिए औसत उम्र 13 से 14 साल मानी जाती है, अब 8 से 11-12 साल में वजन बढ़ने जैसी समस्या आ रही है। कम उम्र में मुश्किल भरे दिनों का सामना करना पड़ रहा है। विशेषज्ञों की मानें तो समस्या प्रदुषण और जंक फूड के अत्यधिक सेवन से बढ़ रही है। शरीर में हार्मोनल परिवर्तन, किसी प्रकार की सिस्ट और ट्यूमर जैसे कारण सामने आ रहे हैं। इनके लिए मुख्य कारण निम्न हैं- लड़कियों में हार्मोनल परिवर्तन से पीरियड जल्दी आते हैं। आनुवंशिक समस्या इसके लिए जिम्मेदार हो सकती है। तनाव से भी हार्मोनल परिवर्तन होते हैं। आयरन तथा विटामिन-डी जैसे पोषण तत्वों की कमी भी हार्मोनल परिवर्तन के लिए जिम्मेदार हैं। प्रदुषण के सम्पर्क में रहने पर भी ये समस्या होती है। शरीर में कही भी सिस्ट या ट्यूमर होने पर भी ये सम्भव है। अगर 8 साल से 12 साल की उम्र के बीच किसी बालिका के शरीर में तेजी से परिवर्तन हो तो मुश्...
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Thick lens and its cardinal points | Optics | General theory of image formation

Thick lens and its cardinal points

Thick lens

  • The combination of two spherical surfaces, is known as thick lens, if the distance between their poles can not be neglected in comparison to their radii.
  • It can be treated as the combination of thin lenses.
  • The thickness of these lenses are comparable to their focal lengths.

Cardinal points of thick lens

  • Let µ = refractive index of material of lens
  • t = thickness of lens
  • R1 and R2 = Radii of curvature of first and second curved surface of the given thick lens.
  • F1 and F2 = First and second focal points respectively.
  • H1 and H2 = First and second principal points respectively.
  • f1 and f2 = First and second focal length of thick lens respectively.

Cardinal points of thick lens

Equivalent focal length

  • If there is same medium on either side of thick lens
  • H1F1 = f1 = - f , and H2F2 = f2 = f

Refraction from surface PP1


Refraction from surface QP2

  • This time I works as an object and forms final image is obtained at F2



  • For thin lens t → 0, and f → f0

Power of thick lens


Position of second focal point (P2F2 = β2)

  • The distance of second focal point will be measured from pole of second refracting surface.

Position of second principal point (P2H2 = α2)

 
  • The distance of second principal point will be measured from pole of second refracting surface

  • Above result is obtained using sign convention.

Position of first focal point (P2F1 = β1)

 
  • For obtaining it we consider that the ray is incident on lens system from right i.e., O՛Q, this time image will be formed on F1. So in β2, R1 is replaced by -R2 and f is replaced by -f.


Position of first principal point (P1H1 = α1)

 
  • For it we use R1 → –R2 and  f → – f in second principal point α2 

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