QUES: Uranium-238 is the most stable isotope of uranium, with a half-life of about 4.468×109 years, roughly the age of the Earth. Uranium-235 has a half-life of about 7.13×108 years, and uranium-234 has a half-life of about 2.48×105 years. For natural uranium, about 49% of its alpha rays are emitted by each of 238U atom, and also 49% by 234U (since the latter is formed from the former) and about 2.0% of them by the 235U. When the Earth was young, probably about one-fifth of its uranium was uranium-235, but the percentage of 234U was probably much lower than this.
What isotope of uranium has the most stability?

ANS: Uranium-238

QUES: Due to extreme variation in elevation, great variation occurs in the climatic conditions of Himachal . The climate varies from hot and subhumid tropical in the southern tracts to, with more elevation, cold, alpine, and glacial in the northern and eastern mountain ranges. The state has areas like Dharamsala that receive very heavy rainfall, as well as those like Lahaul and Spiti that are cold and almost rainless. Broadly, Himachal experiences three seasons: summer, winter, and rainy season. Summer lasts from mid-April till the end of June and most parts become very hot (except in the alpine zone which experiences a mild summer) with the average temperature ranging from 28 to 32 °C (82 to 90 °F). Winter lasts from late November till mid March. Snowfall is common in alpine tracts (generally above 2,200 metres (7,218 ft) i.e. in the higher and trans-Himalayan region).
What occurs in the climatic conditions of Himachal?

ANS: great variation

QUES: Modern police forces make extensive use of radio communications equipment, carried both on the person and installed in vehicles, to co-ordinate their work, share information, and get help quickly. In recent years, vehicle-installed computers have enhanced the ability of police communications, enabling easier dispatching of calls, criminal background checks on persons of interest to be completed in a matter of seconds, and updating officers' daily activity log and other, required reports on a real-time basis. Other common pieces of police equipment include flashlights/torches, whistles, police notebooks and "ticket books" or citations.
What have computers in police cars enabled for reporting?

ANS: updating officers' daily activity log and other, required reports on a real-time basis

QUES: Portugal’s national energy transmission company, Redes Energéticas Nacionais (REN), uses sophisticated modeling to predict weather, especially wind patterns, and computer programs to calculate energy from the various renewable-energy plants. Before the solar/wind revolution, Portugal had generated electricity from hydropower plants on its rivers for decades. New programs combine wind and water: wind-driven turbines pump water uphill at night, the most blustery period; then the water flows downhill by day, generating electricity, when consumer demand is highest. Portugal’s distribution system is also now a two-way street. Instead of just delivering electricity, it draws electricity from even the smallest generators, like rooftop solar panels. The government aggressively encouraged such contributions by setting a premium price for those who buy rooftop-generated solar electricity.
Through what renewable resource had Portugal generated electricity before the solar/wind revolution?

ANS:
hydropower plants on its rivers