Give scientific reasons as to why a clinical thermometer should not be dipped in boiling water?
Answer ::- A clinical thermometer is an ordinary Fahrenheit thermometer, calibrated from 95°F to 110°F, whereas boiling water usually acquires a temperature of more than 100°C or 212°F in water. It is, therefore dangerous to dip a clinical thermometer in boiling water because it is difficult for it to accommodate such high temperature, as a result of which it might burst.
Why is it more difficult to breathe on mountains than on plains?
Answer ::- On the mountains the density of air is much less than in the plains and so the oxygen content for volume is reduced considerably. During the act of breathing a definite supply of oxygen is needed per breathe which being deficient, breathing becomes difficult.
Answer ::- On the mountains the density of air is much less than in the plains and so the oxygen content for volume is reduced considerably. During the act of breathing a definite supply of oxygen is needed per breathe which being deficient, breathing becomes difficult.
Why cloudly nights are warmer than clear nights?
Answer ::- Cloudy nights are warmer than clear nights because clouds prevent radiation of heat from the ground and air.
Answer ::- Cloudy nights are warmer than clear nights because clouds prevent radiation of heat from the ground and air.
A green leaf appears green in daylight but looks dark in red light. Why is it so?
Answer ::- During daylight, a green leaf appears green because out of all the constituents of white light, it reflects green only, all other colours being absorbed. But when red light falls on it, it is all absorbed and hence the green leaf reflects none and looks dark.
Answer ::- During daylight, a green leaf appears green because out of all the constituents of white light, it reflects green only, all other colours being absorbed. But when red light falls on it, it is all absorbed and hence the green leaf reflects none and looks dark.
Why the outer surface of a glass containing iced water becomes wet?
Answer ::- A tumbler containing cold water cools the air near it so that a film of moisture is deposited on the outside of the tumbler by the condensation of water vapours present in the air.
Answer ::- A tumbler containing cold water cools the air near it so that a film of moisture is deposited on the outside of the tumbler by the condensation of water vapours present in the air.
A solar eclipse can occur only on a new moon day. Why?
Answer ::- Soloar eclipse is due to the full moon coming in between the sun and the earth, and hence it is natural that it should be a new moon day.
Answer ::- Soloar eclipse is due to the full moon coming in between the sun and the earth, and hence it is natural that it should be a new moon day.
Why the lunar eclipse occurs only at full moon but not every full moon?
Answer ::- The lunar eclipse occurs only when the moon is full and is near to one of its nodes which does not occur every full moon.
Answer ::- The lunar eclipse occurs only when the moon is full and is near to one of its nodes which does not occur every full moon.
Where days and nights are equal throughout the year and why?
Answer ::- Day and nights are equal throughout the year at the Equator. During the course of the earth’s revolution round the sun, one half of the Equator is always in the light and the other half is in the dark. i.e., the circle of illumination always cuts the Equator into equal parts.
Answer ::- Day and nights are equal throughout the year at the Equator. During the course of the earth’s revolution round the sun, one half of the Equator is always in the light and the other half is in the dark. i.e., the circle of illumination always cuts the Equator into equal parts.
What is the difference between a star and a planet?
Answer ::- Star is the name given to a fixed celestial body which has its own light whereas Planet is the name given to a celestial body which revolves round the sun in elliptical (regular oval shape) orbit. A planet has no light of its own but it reflects light of the sun.
Answer ::- Star is the name given to a fixed celestial body which has its own light whereas Planet is the name given to a celestial body which revolves round the sun in elliptical (regular oval shape) orbit. A planet has no light of its own but it reflects light of the sun.
Where days and nights are longer in the year?
Answer ::- Longest day : 21st June. Longest night 22nd December (in Northern hemisphere).
Answer ::- Longest day : 21st June. Longest night 22nd December (in Northern hemisphere).
Why are mountains cooler than plains?
Answer ::-
Answer ::-
- (i) the air of the mountains is rarer than that of the plains and contains fewer dust particles. The air on the mountains absorbs less heat than the air on the plains,
- (ii) the heat absorbed during the day on the mountains radiates very quickly at night owing to the rarity of the air and nights on the mountains are cooler,
- (iii) due to uneven surface of the mountains, the major portion always remains in the shade. The sun does not heat much of the land which may heat the air.
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