208) The colour of the flame of halide torch, in case of leakage of freon refrigerant, will change to

209) The wet bulb depression indicates __________ humidity of the air.

210) The refrigerant widely used in domestic refrigerators is

211) When absorptivity (?) = 1, reflectivity (?) = 0 and transmittivity (?) = 0, then the body is said to be a

212) Prandtl number (P_N) is given by P_N = ?.c_p/k.