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भारतीय रसायन के पिता आचार्य प्रफुल्ल चंद्र रे की जयंती पर व्याख्यान का आयोजन

भारतीय रसायन के पिता आचार्य प्रफुल्ल चंद्र रे की जयंती पर व्याख्यान का आयोजन विज्ञान भारती उदयपुर इकाई एवं बीएन कॉलेज ऑफ फार्मेसी, बीएन विश्वविद्यालय के संयुक्त तत्वावधान में कार्यक्रम सम्पन्न उदयपुर, 2 अगस्त। भारतीय रसायन के पिता आचार्य प्रफुल्ल चंद्र रे की जयंती के अवसर पर विज्ञान भारती उदयपुर इकाई (चित्तौड़ प्रांत) एवं बीएन कॉलेज ऑफ फार्मेसी, बीएन विश्वविद्यालय के संयुक्त तत्वावधान में एक विशेष व्याख्यान का आयोजन किया गया। कार्यक्रम का उद्देश्य आचार्य पी.सी. रे के वैज्ञानिक योगदान एवं उनके देशभक्ति से ओतप्रोत जीवन पर प्रकाश डालना था। ज्ञातव्य है कि भारत की पहली फार्मा कंपनी आचार्य रे ने ही बंगाल केमिकल एंड फार्मास्यूटिकल्स लिमिटेड, कोलकाता में 1901 में प्रारंभ की थी। कार्यक्रम में विज्ञान भारती के उद्देश्य एवं गतिविधियों की जानकारी डॉ. अमित गुप्ता द्वारा दी गई। आचार्य पी.सी. रे के जीवन और कार्यों पर मुख्य व्याख्यान डॉ. लोकेश अग्रवाल द्वारा प्रस्तुत किया गया। उन्होंने बताया कि कैसे आचार्य रे ने विज्ञान को समाज की सेवा का माध्यम बनाया और रसायन विज्ञान में भारत को आत्मनिर्भर बनान...
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Photo electric effect | Quantum mechanics | Physical basis of quantum mechanics

Photo electric effect

Photo electric effect

  • When light or E.M. radiation of suitable frequency or wavelength falls on a metal surface, it emits electrons.
  • The process of emission of electrons from a metal surface, when illuminated by light of suitable wavelength or frequency is photoelectric effect.
  • The electrons so emitted are photoelectrons.

Experimental Arrangement 

  • T = An evacuated glass tube with a quartz window W
  • P = Photoelectrical sensitive plate
  • C = Hollow cylinder which have a small hole to permit the incident light
  • G = A sensitive galvanometer or ammeter
  • P is connected with negative end of a battery with G
  • C is connected with positive end of a battery

Working

  • When light of suitable frequency falls on P from a source, the photoelectrons are emitted.
  • Since collecting cathode C is connected to positive terminal of battery, so these electrons are attracted towards C.
  • Thus photo electric current (IC) flows from P to C, and this current can be detected or measured by G.
  • IC increases as the potential of C is more and more positive with respect to P.

Laws of photoelectric emission

  • For every metal there is a particular frequency below which there is no photoelectric emission.
  • The minimum frequency required for photoelectric emission is threshold frequency.
  • As the intensity of incident light (IP) increases, IC also increases, i.e. IC ∝ IP.
  • When the frequency of incident light is greater than threshold frequency.

  • On increasing the positive potential of C, IC increases and it become maximum at a particular value of potential.
  • A particular positive potential of collecting cathode C at which the photoelectric current is maximum, is known as saturated current.
  • On increasing the negative potential of C, IC decreases and it become zero at a particular value of potential.
  • The energy of the emitted photoelectrons is independent of intensity of incident light, and depends on the frequency of incident light and nature of the metal.
  • Photoelectric emission is an instantaneous process.


Failure of the electromagnetic theory

  • The calculation shows that the electron take 500 days to eject from sodium by using visible light of wavelength 4000Å, whereas experimentally there is no time delay.
  • According to classical theory, light of greater intensity should impart large kinetic energy to the ejected electrons. But this does not happen.
  • Classical theory shows that the velocity (energy) of the ejected electron should not depend on the frequency of the incident light, but in actual it depends.
To know more about this lecture please visit on https://youtu.be/FeTNKz3RqBc

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