A wire loop enclosing a semi-circle of radius $R$ is located on the boundary of a uniform magnetic field of induction $\overrightarrow{B}.$ At time $t=0$, the loop is set into rotation with velocity $\omega$? about its axis $0$, coinciding with a line of vector $\overrightarrow{B}$ on the boundary as shown in the figure. The emf induced in the loop is

• Correct answer
  A

  $\frac{B{R}^2}{2}\omega$
• B

  $BR\omega$
• C

  $B{R}^2\omega$
• D

  $\frac{B{R}^2}{2\omega }$

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