ISC Physics Class XI Part 1>Chapter 25 - Thermal Radiation>NUMERICALS>Q 14

HARD

11th ICSE

IMPORTANT

Earn 100

The luminosity of Rigel star in Orion constellation is $17000$ times that of the sun. The surface temperature of the sun is $6000 K$ . Calculate the temperature of the star.

Important Questions on Thermal Radiation

HARD

11th ICSE

IMPORTANT

ISC Physics Class XI Part 1>Chapter 25 - Thermal Radiation>NUMERICALS>Q 15

A black body at temperature

300 ° C

radiates

10 J

of heat per sec per sq. cm. of its surface. If the sun is radiating

10^{6} J s^{- 1} {cm}^{- 2}

of its surface, calculate the temperature of the sun.

HARD

11th ICSE

IMPORTANT

ISC Physics Class XI Part 1>Chapter 25 - Thermal Radiation>NUMERICALS>Q 16

A black body radiates energy at the rate of

1.6 \times 10^{6} J m^{- 2} s^{- 1}

. Calculate the temperature at which it will radiate

8.1 \times 10^{6} J m^{- 2} s^{- 1}

.

MEDIUM

11th ICSE

IMPORTANT

ISC Physics Class XI Part 1>Chapter 25 - Thermal Radiation>NUMERICALS>Q 17

The temperature of black body is

727 ° C

and its surface area is

0.1 m^{2}

How many calories the body is emitting per minute.

HARD

11th ICSE

IMPORTANT

ISC Physics Class XI Part 1>Chapter 25 - Thermal Radiation>NUMERICALS>Q 18

The temperature of a filament of a lamp is

2450 K

. Its effective area is

0.048 {cm}^{2}

and its emissivity is

0.30

. Find the wattage of the lamp.

HARD

11th ICSE

IMPORTANT

ISC Physics Class XI Part 1>Chapter 25 - Thermal Radiation>NUMERICALS>Q 19

The temperature of filament of

40 W

bulb is

2284 ° C

and its effective area is

0.66 {cm}^{2}

. The energy radiated by the filament is

0.25

times of a black body of the same area at the same temperature. Calculate the Stefan's constant.

HARD

11th ICSE

IMPORTANT

ISC Physics Class XI Part 1>Chapter 25 - Thermal Radiation>NUMERICALS>Q 20

The temperature of a silver sphere of radius

5 cm is 527 ° C

. If the emissivity is

0.04

find out the energy emitted per sec from the surface of the sphere.

HARD

11th ICSE

IMPORTANT

ISC Physics Class XI Part 1>Chapter 25 - Thermal Radiation>NUMERICALS>Q 21

Calculate the rate of emission in

W {cm}^{- 2}

by a surface at

227 ° C

if its emissivity is

0.6

.

HARD

11th ICSE

IMPORTANT

ISC Physics Class XI Part 1>Chapter 25 - Thermal Radiation>NUMERICALS>Q 22

A metallic blackened sphere of radius of

7 cm

and mass

10 kg

heated to

227 ° C

and suspended in a box maintained at

27 ° C

. Calculate the net rate of heat loss by the sphere. What will be temperature of sphere after

5 \min

? Specific heat of the metal is

420 J {kg}^{- 1} K^{- 1}

.