The graph. Shown in the adjacent diagram, represents the variation of temperature $(T)$ of two bodies, $x$ and $y$ having same surface area, with time $(t)$ due to the emission of radiation. Find the correct relation between the emissivity
IIT 2003, Medium
Download our app for free and get started
(c) Rate of cooling $\left( { - \frac{{dT}}{{dt}}} \right)\; \propto $ emissivity $(e)$
From graph, ${\left( { - \frac{{dT}}{{dt}}} \right)_x} > {\left( { - \frac{{dT}}{{dt}}} \right)_y}$
From graph, ${\left( { - \frac{{dT}}{{dt}}} \right)_x} > {\left( { - \frac{{dT}}{{dt}}} \right)_y}$
==> ${e_x} > {e_y}$
Further emissivity $(e)$ $\propto$ Absorptive power $(a)$
==> ${a_x} > {a_y}$
( good absorbers are good emitters).
Download our appand get started for free
Experience the future of education. Simply download our apps or reach out to us for more information. Let's shape the future of learning together!No signup needed.*
Similar Questions
- 1Heat is flowing through two cylindrical rods of the same material. The diameters of the rods are in the ratio $1 : 2$ and their lengths are in the ratio $2 : 1$. If the temperature difference between their ends is the same, then the ratio of the amounts of heat conducted through per unit time will beView Solution
- 2A cup of coffee cools from $90^{\circ} \mathrm{C}$ to $80^{\circ} \mathrm{C}$ in $\mathrm{t}$ minutes, when the room temperature is $20^{\circ} \mathrm{C}$. The time taken by a similar cup of coffee to cool from $80^{\circ} \mathrm{C}$ to $60^{\circ} \mathrm{C}$ at a room temperature same at $20^{\circ} \mathrm{C}$ is :View Solution
- 3If wavelength of maximum intensity of radiation emitted by Sun and Moon are $0.5 \times 10^{-4} \,m$ and $10^{-4}\,m$ respectively, then the ratio of their temperature is ............View Solution
- 4A hollow copper sphere $S$ and a hollow copper cube $ C$ , both of negligible thin walls of same area, are filled with water at $90°C$ and allowed to cool in the same environment. The graph that correctly represents their cooling isView Solution
- 5A black body radiates at the rate of $W$ watts at a temperature $T$ . If the temperature of the body is reduced to $T/3$ , it will radiate at the rate of (in Watts)View Solution
- 6Two identical plates of different metals are joined to form a single plate whose thickness is double the thickness of each plate. If the coefficients of conductivity of each plate are $2$ and $3$ respectively, then the conductivity of composite plate will beView Solution
- 7A black body radiates energy at the rate of $E$ $W/m^2$ at a high temperature $TK$ . When the temperature is reduced to $\frac{T}{2}K$, the radiant energy will beView Solution
- 8If a metallic sphere gets cooled from ${62^o}C$ to ${50^o}C$ in ${40^o}C$and in the next $10\;\min utes$gets cooled to ${42^o}C$, then the temperature of the surroundings is ......... $^oC$View Solution
- 9The temperature of the body is increased from $-73^o C\, to \,327^o C$, the ratio of energy emitted per second is :View Solution
- 10Two spheres made of same material have radii in the ratio $1: 2$ Both are at same temperature. Ratio of heat radiation energy emitted per second by them isView Solution