wunder · LibraryCHAPTER XV.. 3.--Reflection of Heat.
Read in the Wunder reader — free3.--REFLECTION OF HEAT.
Q. What is meant by REFLECTING HEAT?
A. To reflect heat, is to throw it back in rays from the surface of the reflecting body, towards the place from whence it came.
Q. What are the BEST REFLECTORS of heat?
A. All bright surfaces, and light colours.
Q. Are GOOD ABSORBERS of heat GOOD REFLECTORS also?
A. No; those things which absorb heat best, reflect heat worst; and those which reflect heat worst, absorb it best.
Q. Why are those things which ABSORB HEAT unable to REFLECT it?
A. Because if any thing sucks in heat like a sponge, it cannot throw it off from its surface; and if any thing throws off heat from its surface, it cannot drink it in.
Q. Why are REFLECTORS always made of LIGHT-COLOURED and highly POLISHED METAL?
A. Because light coloured and highly polished metal makes the best of all reflectors.
Q. Why do not PLATE-WARMERS BLISTER and scorch the WOOD behind?
A. Because the bright tin front throws the heat of the fire back again, and will not allow it to penetrate to the wood behind.
Q. If metal be such an excellent CONDUCTOR of heat, how can it REFLECT heat, or throw it off?
A. Polished metal is a conductor of heat, only when that heat is communicated by actual contact; but whenever heat falls upon bright metal in rays, it is reflected back again, and the metal remains quite cool.
Q. What is meant by "heat falling upon metal IN RAYS," and not "by contact"?
A. If a piece of tin were thrust into a fire, it would be in actual contact with the fire; but if it be held before a fire, the heat of the fire falls upon it in rays.
Q. What is the use of the TIN SCREEN or REFLECTOR used in ROASTING?
A. The tin reflector throws the heat of the fire back upon the meat; and, therefore, assists the process of roasting and helps to keep the kitchen cool.
Q. How does a tin REFLECTOR tend to keep the KITCHEN COOL?
A. Because it confines the heat to the hearth, and prevents it from being dispersed throughout the kitchen.
Q. Why does a LAMP GLASS DIMINISH the SMOKE of a LAMP?
A. As glass is a reflector, it reflects the heat of the lamp back upon the flame; in consequence of which, less carbon escapes unconsumed (as smoke).
Q. Why are SHOES HOTTER for being DUSTY?
A. 1st--Because dust absorbs heat: and
2ndly--As it destroys the blackness of our shoes, it prevents them from throwing off the heat of our feet in rays.
Q. Why can we not SEE into the ROAD or STREET, when a CANDLE is lighted in a room?
A. Glass is a reflector; and, therefore, throws the rays of the candle back into the room, and thus prevents our seeing into the road or street.
Q. Why can persons in the DARK STREET see into a ROOM (lighted by a candle or lamp)?
A. The pupil of the eye expands greatly, when persons are in the dark; and, therefore, when any one in the dark street looks into a light room, his dilated pupil sees every thing distinctly.
Q. Why does it always FREEZE on the TOP of a MOUNTAIN?
A. Air is heated by the reflection of the earth, and not by the rays of the sun; and, as there is no earth round a mountain-top to reflect heat, therefore, it remains intensely cold.
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