A plane strip suspended by string on  which monochromatic light is incedent on strip  have power P. Find deflection of string from vertical if strip is perfect black body

• A

  ${\tan }^{-1}\left(\frac{mgc}{P}\right)$

• B

  ${\cos }^{-1}\left(\frac{mgc}{P}\right)$

• C

  ${\tan }^{-1}\left(\frac{P}{mgc}\right)$

• D

  ${\tan }^{-1}\left(\frac{2mgc}{P}\right)$