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1. Photoelectric effect

ph oton. A. ele c tron. K. A. V. P oten t iome ter. 1. Photoelectric effect. Hertz, The photoelectric effect is the emission of electrons when light strikes a surface .

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1. Photoelectric effect

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  1. photon A electron K A V Potentiometer 1. Photoelectric effect Hertz, The photoelectric effect is the emission of electrons when light strikes a surface.

  2. Photocurrent i for a constant light frequency f as a function of the potential VACof the anode with respect to the cathode.

  3. =the minimum energy needed to remove an electron from thesurface • Kmax= ½mv2max = maximum kinetic energy of photoelectrons where h is a universal constant called Planck's constant. Vo = stopping potential

  4. Contohsoal1 Fluksenergimataharisampaikebumiadalah 1,0 x 103 W/m2.. Berapakahcacahfoton yang sampaidibumi per m2tiapdetiknyajikacahayamataharimempunyaipanjanggelombang rata-rata 5000 ? Jawab Energitiapfotondapatdihitung E = h = hc/ = (6,62 x 10-34 Js) (3 x 108 m/s ) /5 x 10-7 m = 4,0 x10-19 J Fluksenergifoton yang sampaidibumi 1,0 x 103 W/m2 =1,0 x 103 Js-1m2 Iniberartienergi yang sampaidibumi per m2tiapdetiknya 1,0 x 103J. Olehkarenaenergitiapfotonadalah 4,0 x10-19 J makacacahfoton yang sampaidibumitiap m2tiapdetikadalahdetiknya 1,0 x 103 J / 4,0 x10-19 J = 2,5 x1021foton.

  5. h Ek B Contohsoal 2 Energi yang diperlukanuntukmelepaselektrondarilogamplatina 9,9 x 10-19 J. Berapakahfrekuensiambangcahayauntukmenghasilkanfotoelektrondariplatinatersebut? Jawab Energifoton yang dijatuhkanpadalogamplatinasebagiandigunakanuntukmelepasikatanelektron (B) dansebagian lain menjadienergikinetikfotoelektron (Ek) GambarFotonmenumbuklogamplatina. Energifoton yang besarnyasamadenganenergi yang dibutuhkanuntukmelepas elektrondariikatannyadisebutenergiambang. Frekuensi yang berkaitandenganenergiambangdisebutfrekuensiambang. Denganmenggunakan E = -B + hatau h = E + B dimana E adalahenergikinetikelektron. Jika E = 0 maka h = B disebutenegiambangatauho = B atau o = B/h = 9,9 x 10-19 J / 6,62 x 10-34 Js = 1,5 x1015 Hz

  6. Time Dilation, Time Comparisons • Observer O measures a longer time interval than observer O’

  7. The Twin Paradox – The Situation • A thought experiment involving a set of twins, Speedo and Goslo • Speedo travels to Planet X, 20 light years from earth • His ship travels at 0.95c • After reaching planet X, he immediately returns to earth at the same speed • When Speedo returns, he has aged 13 years, but Goslo has aged 42 years

  8. Length Contraction – Equation • Length contraction takes place only along the direction of motion

  9. Relativistic Momentum • To account for conservation of momentum in all inertial frames, the definition must be modified • v is the speed of the particle, m is its mass as measured by an observer at rest with respect to the mass • When v << c, the denominator approaches 1 and so p approaches mv

  10. Relativistic Energy • The definition of kinetic energy requires modification in relativistic mechanics • KE = mc2 – mc2 • The term mc2 is called the rest energy of the object and is independent of its speed • The term mc2 is the total energy, E, of the object and depends on its speed and its rest energy

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