A question?

we all know that usually we use black and opaque paper for experiment right? but why can't we use other opaque paper like dark purple or yellow???

others form of energy

If energy used in Singapore (oil and natural gas) were depleted we can use renewable energy such as:
· Solar energy(solar panels)
· Wind energy (windmills, wind turbines)
· Tidal energy/wave energy(from a dam)
· Biofuels(plant) used in cars as petrol

Renewable energy now produce 13% of the world electrical:
Hydropower 2-3% and others including wind, solar, and marine energy together - less than 1%

Singapore average daily max temp: 30.9ºC / average daily temp: 23.9ºC
1) Solar panels which can produce 115watt of electricity cost average $640.
2) Shortage of land to build a solar energy power station.
Wind energy is a clean fuel source. Wind is actually a form of solar energy caused by the heating of the atmosphere by the sun, the rotation of the earth, and the earth's surface irregularities. It is intermittent (not constant)Biofuels can be defined as solid, liquid, or gas fuel derived from biomass.
The first batch of biofuels used new plants natural sugar to make biofuels. This may lead to shortage of food as we do not have any extra land for growing our crops.
Examples of plant ethanol: sugar beets, sugar cane, corn, wheat and barley. Most trees and grasses are made of cellulose, which can also be converted into sugar, although not as easily as starch.