Question

A coil of inductance $0.4mH$ is connected to a capacitor of capacitance $400pF$. To what wavelength is the circuit tuned?

• A. 750m
• B. 751m
• C. 752m
• D. 753m

Answer 1

Answer: (D)

$L=0.4mH=0.4\times 10^{-3}H$
$C=400pF=4\times 10^{-10}F$
$\lambda =?$
$v=\frac{1}{2\pi \sqrt{LC}}$
$v=\frac{1}{2\times 3.14\times \sqrt{0.4\times 10^{-3}\times 4\times 10^{-10}}}$
$v=\frac{10^7}{6.28\times 4}Hz$
If $c$ is velocity of em waves, then
$\lambda =\frac{c}{v}=\frac{3\times 10^8}{10^7/6.28\times 4}$
$\lambda =6.28\times 10\times 4\times 3$
$\lambda =753.6m$