A signal is to be transmitted through a wave of wavelength $\lambda ,$ using a linear antenna. The length $l$ of the antenna and effective power radiated $P_{\mathrm{eff}}$ will be given, respectively, as-
($K$ is a constant of proportionality)

• A

  $\frac{\lambda }{8}, P_{\mathrm{eff}}=K\left(\frac{l}{\lambda }\right)$
• B

  $\frac{\lambda }{16}, P_{\mathrm{eff}}=K{\left(\frac{l}{\lambda }\right)}^3$
• C

  $\frac{\lambda }{5}, P_{\mathrm{eff}}=K{\left(\frac{l}{\lambda }\right)}^{\frac{1}{2}}$
• Correct answer
  D

  $\lambda , P_{\mathrm{eff}}=K{\left(\frac{l}{\lambda }\right)}^2$

Hence, the correct answer is option: 'D'.