**Question:**

**Which of the following is more close to a black body?**

black board paint

green leaves

black holes

red roses

Question of from chapter.

JEE Main Previous Year 2002

Correct Option: 1

**Solution:**

### Related Questions

Two different wires having lengths $L_{1}$ and $L_{2}$, and respective temperature coefficient of linear expansion $\alpha_{1}$ and $\alpha_{2}$, are joined end-to-end. Then the effective temperature coefficient of linear expansion is:

When the temperature of a metal wire is increased from $0^{\circ} \mathrm{C}$ to $10^{\circ} \mathrm{C}$, its length increased by $0.02 \%$. The percentage change in its mass density will be closest to :

At $40^{\circ} \mathrm{C}$, a brass wire of $1 \mathrm{~mm}$ radius is hung from the ceiling. A small mass, $M$ is hung from the free end of the wire. When the wire is cooled down from $40^{\circ} \mathrm{C}$ to $20^{\circ} \mathrm{C}$ it regains its original length of $0.2 \mathrm{~m}$. The value of $\mathrm{M}$ is close to:

(Coefficient of linear expansion and Young’s modulus of brass are $10^{-5} /{ }^{\circ} \mathrm{C}$ and $10^{11} \mathrm{~N} / \mathrm{m}^{2}$, respectively; $g=10 \mathrm{~ms}^{-2}$ )

Two rods $\mathrm{A}$ and $\mathrm{B}$ of identical dimensions are at temperature $30^{\circ} \mathrm{C}$. If $A$ is heated upto $180^{\circ} \mathrm{C}$ and $B$ upto$\mathrm{T}^{\circ} \mathrm{C}$, then the new lengths are the same. If the ratio of the coefficients of linear expansion of $\mathrm{A}$ and $\mathrm{B}$ is $4: 3$, then the value of T is:

A thermometer graduated according to a linear scale reads a value $x_{0}$ when in contact with boiling water, and $x_{0} / 3$ when in contact with ice. What is the temperature of an object in ${ }^{\circ} \mathrm{C}$, if this thermometer in the contact with the object reads $\mathrm{x}_{0} / 2 ?$

A rod, of length $L$ at room temperature and unıform area of cross section A, is made of a metal having coefficient of linear expansion $\alpha /{ }^{\circ} \mathrm{C}$. It is observed that an external compressive force $\mathrm{F}$, is applied on each of its ends, prevents any change in the length of the rod, when its temperature rises by $\Delta \mathrm{T} K$. Young’s modulus, $\mathrm{Y}$, for this metal is:

An external pressure $\mathrm{P}$ is applied on a cube at $0^{\circ} \mathrm{C}$ so that it is equally compressed from all sides. $\mathrm{K}$ is the bulk modulus of the material of the cube and $\alpha$ is its coefficient of linear expansion. Suppose we want to bring the cube to its original size by heating. The temperature should be raised by:

A steel rail of length $5 \mathrm{~m}$ and area of cross-section 40 $\mathrm{cm}^{2}$ is prevented from expanding along its length while the temperature rises by $10^{\circ} \mathrm{C}$. If coefficient of linear expansion and Young’s modulus of steel are $1.2 \times 10^{-5} \mathrm{~K}^{-1}$ and $2 \times 10^{11} \mathrm{Nm}^{-2}$ respectively, the force developed in the rail is approximately:

A compressive force, $F$ is applied at the two ends of a long thin steel rod. It is heated, simultaneously, such that its temperature increases by $\Delta \mathrm{T}$. The net change in its length is zero. Let $l$ be the length of the rod, $\mathrm{A}$ its area of cross-section, $Y$ its Young’s modulus, and $\alpha$ its coefficient of linear expansion. Then, $\mathrm{F}$ is equal to:

The ratio of the coefficient of volume expansion of a glass container to that of a viscous liquid kept inside the container is $1: 4$. What fraction of the inner volume of the container should the liquid occupy so that the volume of the remaining vacant space will be same at all temperatures?