(a) Why is the solar cooker box covered with a plane glass plate?
(b) Why is energy of water flowing in a river considered to be an indirect form of solar energy?
(a) The solar cooker box is covered with a plane glass plate so as to prevent heat from
escaping.
(b) Sun is said to be the ultimate and the original source for most of the energy present on the Earth. When sun rays fall on oceans and other water bodies, the water present in the water bodies gets evaporated and rises up in the atmosphere. In the upper part of the atmosphere, this water vapour gets condensed and forms clouds, which give rain on the high lands. Therefore, the rain water runs over the land surface towards the large water bodies. This running water over the land surfaces is called river. Therefore, the energy of running water actually originates from the solar energy.
This is why solar energy of water flowing in a river is considered to be an indirect form of solar energy.
The fission of nucleus is brought about by splitting the nucleus of heavy atoms, such as uranium or plutonium, with low-energy neutron bombardment.