Questions

World Population day is an annual event, observed on July 11 every year, which seeks to raise awareness of global population issues. 

A device which is used to convert light energy directly into electrical energy is called as photovoltaic cell or a solar cell.

Heliostats convert light energy into heat energy.

A thermocouple is a device for measuring temperature.

The absence of a landmass within these latitudes in the southern hemisphere eliminate friction and lends force to these winds and hence derives the name

Robert Brown, Scottish botanist, Discovered The Nucleus of a Cell in 1831, London. When Brown was studying orchids under microscope when he observed an opaque area, which he called the "Areola" or "Nucleus", in the cells of the flower's outer layer.

The nucleus was also described by Franz Bauer in 1804 but in detail Robert Brown made it in 1831.

Hydroelectricity is electricity produced from hydropower i.e, water.