Given, the angular velocity, ω=602π×120rads−1.
Recall the formula of induced EMF in terms of angular velocity and radius of the ring, ϵ=21Bωr2, now put the proper values at proper places,
⇒ϵ=21×(0.4×10−4)×(2π[60120])(1)2
⇒ϵ=0.8π×10−4=2.512×10−4V.