Assertion (A): In a furnace, radiation from the walls has the samewave...
Ans. (d) Wall and furnace has different temperature.
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Assertion (A): In a furnace, radiation from the walls has the samewave...
Assertion (A): In a furnace, radiation from the walls has the same wavelength as the incident radiation from the heat source.
Reason (R): Surfaces at the same temperature radiate at the same wavelength.
The correct answer is option D, i.e., Assertion (A) is false but Reason (R) is true.
Explanation:
Assertion (A): In a furnace, radiation from the walls has the same wavelength as the incident radiation from the heat source.
Radiation is the transfer of energy through electromagnetic waves. In a furnace, heat is generated by a heat source, such as burning fuel or electric heating elements. This heat source emits radiation, which transfers energy to the surroundings, including the walls of the furnace.
The wavelength of radiation emitted by a heat source depends on its temperature. According to Planck's law, the wavelength of maximum radiation (peak wavelength) is inversely proportional to the temperature of the radiating body. As the temperature of the heat source increases, the peak wavelength decreases.
The assertion states that the radiation from the walls of the furnace has the same wavelength as the incident radiation from the heat source. However, this is not necessarily true. The walls of the furnace can be at a different temperature than the heat source. If the walls are at a lower temperature, they will emit radiation with a longer wavelength than the incident radiation from the heat source. On the other hand, if the walls are at a higher temperature, they will emit radiation with a shorter wavelength than the incident radiation.
Therefore, Assertion (A) is false.
Reason (R): Surfaces at the same temperature radiate at the same wavelength.
The reason states that surfaces at the same temperature radiate at the same wavelength. This statement is true and is known as Wien's displacement law. According to this law, the wavelength of maximum radiation emitted by a black body is inversely proportional to its temperature. In other words, if two surfaces are at the same temperature, they will emit radiation with the same wavelength of maximum radiation.
This is why objects at room temperature emit radiation in the infrared range, which is longer wavelength than visible light. Objects at higher temperatures, such as the sun or a burning flame, emit radiation in the visible or even ultraviolet range.
Therefore, Reason (R) is true.
In conclusion, Assertion (A) is false because the radiation from the walls of a furnace may have a different wavelength than the incident radiation from the heat source. However, Reason (R) is true because surfaces at the same temperature do radiate at the same wavelength.
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