(A) For independent events:
\[ P(A \cap B) = P(A) \cdot P(B) = 0.5 \cdot 0.4 = 0.2. \](B) Using the formula:
\[ P(A \cup B) = P(A) + P(B) - P(A \cap B). \]Substituting values:
\[ P(A \cup B) = 0.5 + 0.4 - 0.2 = 0.7. \]State Gauss's Law in electrostatics. Using it (i) find electric field due to a point source charge \( q \) and (ii) deduce Coulomb's law between source charge \( q \) and test charge \( q_0 \).
Compare features of p-type and n-type semiconductors. Draw circuit diagram of half-wave rectifier of p-n junction diode and explain it.
What is atomic model of magnetism? Differentiate between paramagnetic, diamagnetic, and ferromagnetic substances on this basis. Also, give one example of each.