True or Flase Photonics is the base for the field of optics.

ad sM vunM lo livsbil A laisibul Question 3 Engineers and scientists often use eneray band diagrams to graphically illustrate ihe energy levels of electrons in different substances. Electrons are shown ds Conduction band Some metals Valence band (untiled Conduction band Other metals Overlap Valence band Energy gap Conauction band Semiconductors (intrinsic) Valence band Energy gap Conduction band alori-noitbelo Insulators Valence band solid dots: Based on these diagrams, answer the following questions: Which type of material is the best conductor of electricity, and why? 2 Which type of material is the worst conductor of electricity, and why? Question 4

Q2/ Prove that Pp E - E, = kT In %3D 'fp

A zener diode when biased correctly A- acts as a fixed resistance B- never overheats C- has a constant voltage across it D- has a constant current passing through it Light of wavelength A falls on a metal with work-function hc/ho . Photoelectric effect will take place only if B-12 2h0 D-1<20 /2

The angle of conduction of the freewheeling diode in the circuit shown = Thl Th2 240V RMS DM A (O DC Motor D1 D2 O e = 2(180 '- a) %3D O e = 3a %3D O e = 3(180- a) %3D e 2(90 a) !! O @ = 2a %3D O e= 2(360 - a)

Task 3 The circuit shown is used to rectify the AC voltage u(t). The characteristic curve of the diode is shown on the right. Given values: u(t)=6 V cos(2m 1 kHz () R = 510 Rv=47 02 U₁ = 26 mV Ry us(t) A RL 4₂ (1) (A) 1 10 10⁰ L 20 0 Labe T-25°C V, 0.4 0.6 0.8 1.0 1.4 Forward characteristics (typical values) a) The diode can be described by the equation /=/e. Determine approximately the value of m from the characteristic curve for Tj= 25°C. 4P

Why is it desirable to wait 1 s after a potential pulse before recording the current in voltammetry?

A diode has IS = 10−17 A and n = 1.05. (a) What is the diode voltage if the diode current is 70 μA? (b) What is the diode voltage if the diode current is 5 μA? (c) What is the diode current for vD =0 V? (d) What is the diode current for vD =− 0.075 V? (e) What is the diode current for vD =−5 V?

A gallium arsenide semiconductor at T = 300 K is homogeneously doped with Nd= 5 X 1016 cm-3 and N₂ = 0. Calculate the a drift current for an applied E field of 20 V/cm Jdrf = 1360 A/cm² Jdrf = 2432 A/cm² drf = 624 A/cm² Jdrf=512 A/cm²

For the RC circuit in figure 3: (a) what is the current in the capacitor 2.30 seconds after the switch is closed? (b) What is the power supplied by the battery 1.30 seconds after the switch is closed?