A light ray passes from air (n1=1.00) into water, where the refractive index n2 changes slowly with temperature. At one instant θ1=30∘, θ2=20∘, and n2 is increasing at 0.002s−1. The angle θ1 is increasing at 0.010rad/s. According to the law of refraction, what is the instantaneous rate of change of the angle of refraction, dθ2/dt, at that instant?
a) +6.3×10−3rad/s
b) −5.8×10−3rad/s
c) +5.8×10−3rad/s
d) +4.2×10−3rad/s