Question 378: Properties of Matter

Question

A piece of iron is heated in a flame. It first becomes dull red then becomes reddish yellow and finally turns to white hot. The correct explanation for the above observation is  possible by using

Accepted Answer

According to WienÃ¢ÂÂs displacement law
$${\lambda _m}T$$ = constant
$${\lambda _m} = {{constant} \over T}$$
So when a piece of iron is heated, $${\lambda _m}$$ decreases i.e. with rise in temperature the maximum intensity of radiation emitted gets shifted towards the shorter wavelengths. So the colour of the heated object will change that of longer wavelength (red) to that of shorter (reddish yellow) and when the temperature is sufficiently high and all wavelengths are emitted, the colour will become white.

Answer

Kirchhoff's Law

Answer

Newton's Law of cooling

Answer

Stefan's Law

Answer

Wien's displacement Law

Properties of Matter

A piece of iron is heated in a flame. It first becomes dull red then becomes reddish yellow and finally turns to white hot. The correct explanation for the above observation is possible by using

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