MCQ
A hot body will radiate heat most rapidly if its surface is
- AWhite & polished
- BWhite & rough
- CBlack & polished
- ✓Black & rough
✓
Answer
Correct option: D.
Black & rough
d
(d)Black and rough surfaces are good absorber that’s why they emit well. (Kirchoff's law).
(d)Black and rough surfaces are good absorber that’s why they emit well. (Kirchoff's law).
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
In $a$ one-dimensional collision, $a$ particle of mass $2m$ collides with $a$ particle of mass $m$ at rest. If the particles stick together after the collision, what fraction of the initial kinetic energy is lost in the collision?
→Two sources of sound $S_1$ અને $S_2$ are moving towards and away from a stationary observer with the same speed respectively. Observer detects $3$ beats per second. Find speed of source (approximately). (in $m/s$)
→Given, $F 1= F 2=500\, Hz$. speed of air $=330\, m / s$
The maximum range of a gun on horizontal terrain is $16 \,km$. If $g = \;10m/{s^2}$. What must be the muzzle velocity of the shell ......... $m/s$
→A ball is bouncing elastically with a speed 1m/s between walls of a railway compartment of size 10m in a direction perpendicular to walls. The train is moving at a constant velocity of 10m/s parallel to the direction of motion of the ball. As seen from the ground,
- The direction of motion of the ball changes every 10 seconds.
- Speed of ball changes every 10 seconds.
- Average speed of ball over any 20 second interval is fixed.
- The acceleration of ball is the same as from the train.
A gravitational field is present in a region and a mass is shifted from $A$ to $B$ through different paths as shown. If $W _1, W _2$ and $W _3$ represent the work done by the gravitational force along the respective paths, then
→Two particles of equal mass have velocities $2\,\hat i\, ms^{-1}$ and $2\,\hat j\, ms^{-1}$. First particle has an acceleration $(\,\hat i\, + \,\hat j\,)$ $ms^{-2}$ while the acceleration of the second particle is zero. The centre of mass of the two particles moves in
→Spring of spring constant $1200\, Nm^{-1}$ is mounted on a smooth frictionless surface and attached to a block of mass $3\, kg$. Block is pulled $2\, cm$ to the right and released. The angular frequency of oscillation is .... $ rad/sec$
→A beaker contains a fluid of density $\rho \, kg / m^3$, specific heat $S\, J / kg\,^oC$ and viscosity $\eta $. The beaker is filled upto height $h$. To estimate the rate of heat transfer per unit area $(Q / A)$ by convection when beaker is put on a hot plate, a student proposes that it should depend on $\eta \,,\,\left( {\frac{{S\Delta \theta }}{h}} \right)$ and $\left( {\frac{1}{{\rho g}}} \right)$ when $\Delta \theta $ (in $^oC$) is the difference in the temperature between the bottom and top of the fluid. In that situation the correct option for $(Q / A)$ is
→The maximum possible efficiency of a heat engine is ...........
The apparent coefficient of expansion of a liquid when heated in a brass vessel is $X$ and when heated in a tin vessel is $Y$. If $\alpha$ is the coefficient of linear expansion for brass, the coefficient of linear expansion of tin is ..........
→