Modern Physics 6 Question 22
24. A diode detector is used to detect an amplitude modulated wave of $60 %$ modulation by using a condenser of capacity $250 pF$ in parallel with a load resistance $100 k \Omega$. Find the maximum modulated frequency which could be detected by it.
(2013 Main)
(a) $10.62 MHz$
(b) $10.62 kHz$
(c) $5.31 MHz$
(d) $5.31 kHz$
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Solution:
The higher frequency which can be detected with tolerable distortion is
$$ \begin{aligned} f & =\frac{1}{2 \pi m _a R C}=\frac{1}{2 \pi \times 0.6 \times 2.5 \times 10^{-5}} Hz \\ & =\frac{100 \times 10^{4}}{25 \times 1.2 \pi} Hz=\frac{4}{1.2 \pi} \times 10^{4} Hz=10.61 kHz \end{aligned} $$
