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SS3: PHYSICS - 2ND TERM

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  1. Magnetic Field | Week 1
    4 Topics
  2. Electromagnetic Field
    4 Topics
  3. Electromagnetic Induction
    6 Topics
  4. The Transformer
    5 Topics
  5. Simple A.C Circuit
    4 Topics
  6. Models of the Atom
    2 Topics
  7. Radioactivity
    3 Topics
  8. Half Life
    8 Topics
  9. Energy Quantization
    3 Topics
  10. Photoelectric Effect
    4 Topics
  11. Wave Particle Paradox
    3 Topics



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Einstein proposed that light waves consist of packets of energy called quanta or photons and each photon has an energy, hf, h is Plank’s constant (6.6 x 10-34Js) and f is the frequency of the light i.e E = hf = \( \frac{hc}{\lambda} \)

The incident light must produce enough energy for electrons to overcome the electrostatic force of the metal. The workdone by an incident light to remove electrons from a metal is called work function (w)

Work function is the maximum energy needed to liberate an electron from a metal surface.

Using Einstein relation

W0 = Work function

hf = W0 + \( \frac{1}{2} \scriptsize mv^2\)

hf = hf0 + \( \frac{1}{2} \scriptsize mv^2\)

mv2 = hf – W0

∴hf = hf0 + E

E = \( \frac{1}{2} \scriptsize mv^2\) – Kinetic energy of the photoelectrons.

E = hf – hf0

This is known as Einstein’s photoelectric equation.

E = \( \frac{1}{2} \scriptsize mv^2\)= eV

\( \frac{1}{2} \scriptsize mv^2\) = eV

eV is electron volt.

∴ E = eV = hf – hf0

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