In communication system, the range for line of sight propagation in case of earth is 'd', for the height of antenna (h). If 'h' is doubled then the new range is

• A

  $\frac{\mathrm{d}}{\sqrt{2}}$
• B

  $\frac{\sqrt{2}}{\mathrm{~d}}$
• C

  $\frac{\mathrm{d}}{2}$
• Correct answer
  D

  $\sqrt{2} \mathrm{~d}$

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