electrons waves and photons

electrons waves and photons

1. charge and current

   • equations
     • I = Anev
       • where v is velocity
   • 1 amp = 1 coulomb of charge passing a given point a second
   • in metals electrons travel from -ve --> +ve
     • the direction of conventional current is the opposite
   • Kirchhoff's 1st - the sum of the currents into a point is equal the the sum of the currents out

2. waves

   • progressive
     • transfer energy not matter
     • particles vibrate parallel to the direction of energy transfer
   • transverse
     • oscillations or vibrations are perpendicular to the direction of energy transfer
     • has peaks and troughs
   • longitudinal
     • oscillations are parallel to direction of energy transfer
     • sound waves
   • equations
     • intensity = p/A
     • n=c/v
       • n is the reflective index
   • phase diff
     • 360 degrees = in phase
     • 180 degrees = anti phase
   • reflection - angle of incidence = angle of reflection
   • total internal reflection conditions
     • high refractive index to a low refractive index
     • angle is strikes boundary > critical angle
   • path diff
     • n wavelengths = arrive in phase
     • n +1/2 wavelengths = arrive in antiphase
   • stationary waves

3. energy power and resistance

   • equations
     • v=w/Q
   • e.m.f = work done on the charge carriers
   • p.d = work done by the charge carriers
   • electron gun pg 143 double book
   • ohms law - for a metallic conductors at a constant temperature current is directly proportional to P.d
   • increase in temp leads to increased resistance
   • thermistor - resistance decreases as temp increases
   • LDR - low resistance in bight conditions

4. electrical circuits

   • equations
   • kirchhoff's 2nd - sum of e.m.f = sum of P.d in a closed loop
   • series
     • current is the same in every position
     • sum of e.m.f = sum of P.d
     • R = R1 + R2 ...
   • parallel
     • current is split per branch
     • sum of e.m.f = sum of P.d per branch
     • 1/R = !/R1 +1/R2 ...

5. quantum physics

   • equations
   • 1 eV = 1.6 * 10-19 J
   • photoelectric effect - key observations
     • photoelectrons were only emitted if the incident radiation is above the threshold frequency
     • when radiation> f0
       • emission is instantaneous
       • increasing intensity increased amount of electrons emitted
       • increase in freq = increase in KE

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