Which glass is usually used in optical work?

The half life period of a radioactive element depends on its ________?

Liquid ammonia and 60% nitric acid reaction (which produces ammonium nitrate) is________?

The space time is equivalent to the holding time in a steady state mixed reactor for________?

Pick out the wrong statement?

The inner wall of a furnace is at a temperature of 700°C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m-1.°C- 1 respectively. The ambient air is at 30°C and the heat transfer co-efficient between the outer surface of wall and air is 20 W.m-2.°C-1. The rate of heat loss from the outer surface in W.m-2is________?