Lummer and Pringsheim performed experiments in 1899, to study the distribution of energy with the wavelength in spectrum of black body radiations. The intensity of black body radiations corresponding to wavelength ranging from zero to infinity is measured and plotted at various temperatures of black body. The intensity verses wavelength graph is called spectrum.

1) At given temperature of black body:-

The energy emitted is not distributed uniformly among all wavelengths.

The energy emitted is maximum for wavelength λmax and it falls on either side of it. The wavelength is called wavelength of maximum emission.

2.) With rise in temperature of black body:-

The energy emitted increases rapidly for any wavelength.

The wavelength for which energy emitted is maximum and shifted towards left of X-axis Or the  i.e. wavelength for which energy emitted is maximum is inversely proportional to its abosolute temperature.

λmax T= b(constant), where b= Wien’s constant= 2.9х10-3 m.K.

Wien’s displacement law:- The wavelength (λmax) corresponding to maximum energy emitted by a black body is inversely proportional to its absolute temperature. Q.1) Who studied the spectrum of black body radiation?

a) Ferry

b) Maxwell

c) Stefan

d) Pringsheim

Q.2)  The distribution of energy of black body at given temperature is….

a) uniform

b) non uniform

c) straight line

d) none of these.

Q.3) The magnitude of wavelength for which maximum energy emitted by black body is……

a) decrease with increase in temperature

b) increases with increase in temperature

c) unchanged with temperature

d) both ‘a’ and ‘b’

Q.4) The wavelength for which energy is maximum is……

a) directly proportional to absolute temperature

b) inversely proportional to absolute temperature

c) unchanged with temperature

d) cannot predicted

Q.5) The value of Wien’s constant is given as….

a) 2.9х10-3 K

b) 2.9х10-5 K

c) 2.9х10-5 K

d) 2.9х10-3 K

Q.6) Which of the following graph represents the correct representation for variation of energy with wavelength for black body radiation? a) fig.1

b) fig.2

c) fig.3

d) fig.4

Q.7) The wavelength of radiation if temperature of black body is 10000K……..

a) 2.9×10-3 m

b) 2.9×10-6 m

c) 2.9×10-3 cm

d) 2.9×10-6 cm Q.8) If wavelength for which the maximum energy emitted by black body is 6590 A0, the temperature of black body is…..

a) 44000K

b) 4400K

c) 440K

d) 4.40 0K Q.9) If the ratio of maximum wavelength for black body radiation is 5:8, the ratio of temperature for the black bodies is….

a) 5:8

b) 2:3

c) 8:5

d) 3:2

Q.1) d) Pringsheim

Q.2) b) non uniform

Q.3) a) decrease with increase in temperature

Q.4) b) inversely proportional to absolute temperature

Q.5) d) 2.9х10-3 m. K

Q.6) c) fig.3

Q.7) b) 2.9 × 10-6  m

Q.8) a) 44000K

Q.9) c) 8:5

Updated: June 30, 2021 — 12:17 am