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Important Questions on Thermal Properties of Matter

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Radiation

On observing light from three different stars

P

Q

and

R

, it was found that intensity of violet colour is maximum in the spectrum of

P

, the intensity of green colour is maximum in the spectrum of

R

and the intensity of red colour is maximum in the spectrum of

Q

. If

T_{p}, T_{Q}

and

T_{R}

are the respective absolute temperatures of

P

Q

and

R

, then it can be concluded from the above observations that :

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Radiation

The wavelength of thermal radiation is

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Radiation

A heat source at

T = 10^{3} K

is connected to another heat reservoir at

T = 10^{2} K

by a copper slab which is

1 m

thick. Given that the thermal conductivity of copper is

0 .1 W K^{- 1} m^{- 1}

, the energy flux through it in the steady-state is:

EASY

Physics>Heat and Thermodynamics>Thermal Properties of Matter>Radiation

The unit of thermal conductivity is

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Radiation

Let there be four identical cubes having colours blue, red, black and white. When they are heated together and allowed to cool under identical conditions, which cube will cool at the earliest?

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Radiation

Two rods A and B of different materials are welded together as shown in figure. Their thermal conductivities are $K_{1}$ and $K_{2}$ . The thermal conductivity of the composite rod will be

Question Image

MEDIUM

Physics>Heat and Thermodynamics>Thermal Properties of Matter>Radiation

Heat energy is incident on the surface of a material at the rate of

1000 J \min^{- 1}

. If the coefficient of absorption is

0.8

and the coefficient of reflection is

0.1

, then the amount of heat energy transmitted through the material in

5 minutes

EASY

Physics>Heat and Thermodynamics>Thermal Properties of Matter>Radiation

Ordinary bodies

A

and

B

radiate maximum energy with wavelength difference

4 μ m

. The absolute temperature of body

A

3

times that of

B

. The wavelength at which body

B

radiates maximum energy is

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Radiation

Two spherical black bodies have radii

r_{1}

and

r_{2}

. Their surface temperatures are

T_{1}

and

T_{2}

. If they radiate same power then

\frac{r_{2}}{r_{1}}

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Radiation

In Raman effect, the spectral line with lower frequency than the incident frequency is

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Radiation

If temperature of a black body increases from

300 K

900 K

, then the rate of energy radiation increases by

HARD

Physics>Heat and Thermodynamics>Thermal Properties of Matter>Radiation

Three large identical plates are kept parallel to each other. The outer two plates are maintained at temperatures

T

and

2 T

, respectively. The temperature of the middle plate in steady state will be close to

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Radiation

Three rods of identical cross-sectional area and made from the same metal, form the sides of an isosceles triangle

A B C

right angled at

B

as shown in figure. The point

A

and

B

are maintained at temperature

T

and

\sqrt{2} T

respectively, in the steady state. Now, assuming that only heat conduction takes place. The temperature of point

C

will be

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Radiation

The two ends of a metal rod are maintained at temperatures

100 ° C

and

110 ° C

. The rate of heat flow in the rod is found to be

4.0 J s^{- 1}

. If the ends are maintained at temperatures

200 ° C

and

210 ° C

, the rate of heat flow will be:

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Radiation

Statement $A :$ Convection involves flow of matter within a fluid due to unequal temperatures of its parts.

Statement $B :$ A hot bar placed under a running tap water loses heat due to effect of convection within water.

Statement. $C :$ Heat transfer always involves temperature difference between two systems.

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Radiation

The freezer in a refrigerator is located at the top section so that

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Radiation

A black body has maximum wavelength

λ_{m}

at temperature

2200 K .

Its corresponding wavelength at temperature

3300 K

will be

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Radiation

A certain planet is at

a

distance

d

from the sun. Then the temperature of the planet is

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Radiation

(A)	The energy emitted versus wavelength plot of a black body depends on the material of the black body.
(B)	The emissivity of a completely reflecting surface is zero.
(C)	Emissivity is equal to ${(absorptive power)}^{2}$ .
(D)	Black-body radiates more than normal body Which of the following is correct?

EASY

Physics>Heat and Thermodynamics>Thermal Properties of Matter>Radiation

For any material, if

R, T

and

A

represent the reflection coefficient, transparent coefficient and absorption coefficient respectively, then for a blackbody which one of the following is true

A perfect black body is one whose emissive power is

Important Questions on Thermal Properties of Matter

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