Question 1. What is non-renewable energy source? Give any two examples.
Answer: Energy sources which are not recovered after being spent. It is called non-renewable energy source. Like coal, petrol etc. are non-renewable energy sources.
Question 2. Explain the difference between convex and concave lenses.
Answer-Difference between convex lens and concave lens-
convex lens
1. Its refraction surface is convex.
2. In this both real and virtual images are formed.
3. The middle part of a convex lens is thick and the edge is thin.
concave lens
1. Its refractive surface is sunken.
2. Only virtual image is formed in these.
3. Its middle part is thin and the edge part is thick.
Question 3. Of the eyes. What is meant by adjustment capacity?
Answer: The ability of the objective lens, by which the focal length of the lens is increased or decreased to clearly see objects placed at different distances, is called accommodation ability. For normal vision, accommodation in young adults is between 25 cm and infinity, so the accommodation power is 4 diopters.
Question 4. What is geothermal energy?
Answer: Energy generated from hot water sources beneath the earth's surface is called geothermal energy.Question
5. Explain how water energy can be converted into electrical energy? Also write two benefits of water energy.
Answer-Hydroelectricity- Generation of electricity by using the power of flowing water is one of the major alternative sources of energy. The water of the fast flowing river is collected in a high dam. On the other side of the dam, several meters below, there is a turbine, which is connected to a generator. The water flowing through the dam gate provides power which drives the turbine and produces electricity. Energy obtained from hydropower is also renewable energy.
Benefits - (i) Due to this, we get one-fourth of the total energy obtained from water energy.
(ii) With water energy we use electric motors, generators, fans and lights in our homes. It is also used as road light on roads.
