11) Why the green house operators paint their glass roofs white in summer?
Ans: White colour is the reflector of light and it absorbs less heat as compared to other
colours. As in summer there is already very hot season and heat is not required to that level.
That is why the green-house operators paint glass roofs white in summer season.
12) Water boils quicker on mountains.?
Ans: On Mountains the pressure of the air is low due to height, as the air pressure decreases
with altitude. In this way, water boils quicker on mountains at temperature less than 100
degree centigrade, which is the boiling point of water at ground level.
13) Rainbow is produced in the sky after rainfall and sunlight?
Ans: After rain, many droplet of water travel in the atmosphere. When sun rays fall on these
droplets, dispersion of water occurs and droplets act as prism and produce a spectrum of
seven colours. That‘s why a rainbow is seen in the sky after rain.
14) Milk is considered as an ideal food?
Ans: Milk is considered as an ideal food due to following reasons:
a) It contains all constitute of balanced diet.
b) Milk contains fat.
c) Milk has high nutritional value because it contains proteins as well as minerals

15) Lunar eclipse last much longer than solar eclipse?

Ans: Lunar eclipse last longer than the solar eclipse because the length of the earth‘s umbral

shadow cone is more than three times the average distance between the moon and the earth,

so the shadow is relatively wide at the point where the moon crosses it.