A ring of radius r is rotating about its diameter with angular velocity `omega` in a perpendicular magnetic field `vecB` It has 20turns.The emf induced is#fig
Options:
(a) `20Bpi r^2 Sinwt`
(b) `20Bpi r^2 coswt`
(c) `10/sqrt2Bpir^2`
(d) `20B pir wsinwt`