Physics Application( urgent help)

[diwash]

May/June09....Qno 11 (III)
I have done i and ii need help to understand iii

http://www.xtremepapers.me/CIE/International A And AS Level/9702 - Physics/9702_s09_qp_4.pdf

 

[WellWIshER]

guys i dont understand the intensity coefficient part in the question given in da book

y do we multipy .34 by 1/15???