Why should a fuse with defined rating not be replaced by one with a larger rating?

If the refractive index of air with respect to glass is expressed as $^g\mu_a = \dfrac{\text{sin i}}{\text{sin r}}$ answer the following:

(a) Express the similar expression for $^a\mu_g$ in terms of i and r.

(b) If angle r = 90°, what is the corresponding angle (i) is called?

(c) Write down the physical significance of angle (i) in part (b).

The magnetic field produced by a current carrying conductor is shown below. Is there a similar magnetic field produced around a thin beam of moving α-particles and neutrons? Justify your answer.

What do you understand by the following statements?

(a) The heat capacity of the body is 60 JK^-1.

(b) The specific heat capacity of lead is 130 Jkg^-1K^-1