# Wien's Displacement Law

## Trending Questions

**Q.**Thermal radiations are electromagnetic waves belonging to

- ultraviolet region
- visible region
- infrared region
- All of the above

**Q.**The adjoining diagram shows the spectral energy density distribution Eλ of a black body at two different temperatures. If the areas under the curves are in the ratio 16:1, the value of temperature T is

- 32000 K
- 16000 K
- 8000 K
- 4000 K

**Q.**The adjoining diagram shows the spectral energy density distribution Eλ of a black body at two different temperatures. If the areas under the curves are in the ratio 16:1, the value of temperature T is

- 32000 K
- 16000 K
- 8000 K
- 4000 K

**Q.**The energy radiated by a black body at 2300 K is found to have maximum intensity at wavelength 1260 nm, its emissive power being 8000 W/m2. When the body is cooled to a temperature T K, the emissive power is found to decrease to 500 W/m2. Find the wavelength at which intensity of emission is maximum at the temperature T.

- 1575 nm
- 2520 nm
- 1260 nm
- 5040 nm

**Q.**

According to Wien's displacement law wavelength corresponding to maximum intensity decreases when the temperature of blackbody increases.

- False
- True

**Q.**The energy radiated by a black body at 2300 K is found to have maximum intensity at wavelength 1260 nm, its emissive power being 8000 W/m2. When the body is cooled to a temperature T K, the emissive power is found to decrease to 500 W/m2. Find the wavelength at which intensity of emission is maximum at the temperature T.

- 1575 nm
- 2520 nm
- 1260 nm
- 5040 nm

**Q.**Which of the following graphs correctly represents the variation of logλm with logT?

[λm is the wavelength corresponding to maximum intensity of radiation and T represents absolute temperature.]

**Q.**The power radiated by a black body is P and it radiates maximum energy around wavelength λ∘. If the temperature of the black body is now changed so that it radiates maximum energy around a wavelength 3λ∘/4, the power radiated by it will increase by a factor of

- 43

169

6427- 25681

**Q.**Statement 1 : Radiations of longer wavelengths are predominant at lower temperature.

Statement 2 : The wavelength corresponding to maximum emission of radiations shifts from longer wavelength to shorter wavelength as the temperature increases.

- Statement 1 is true, statement 2 is false
- Statement 1 is false, statement 2 is true
- Both Statement 1 and statement 2 are true
- Both Statement 1 and statement 2 are false

**Q.**Distribution of intensity of emitted energy as a function of wavelength is shown in the figure. Point A corresponds to the peak wavelength emitted by a body at certain temperature. Find the correct option when the temperature of the body increases.

- Intensity of A increases, wavelength decreases
- Intensity of A decreases, wavelength decreases
- Intensity of A increases, wavelength increases
- Intensity of A decreases, wavelength increases

**Q.**A black body is at rest at a temperature of 2880 K. The energy of radiation emitted by this object with wavelength between 499 n-m and 500 n-m is U1, between 999 and 1000 nm is U2 and between 1499 nm and 1500 nm is U3. The Wien's constant b=2.88×106 nm-K. Then

- U1=0
- U3=0
- U1>U2
- U2>U1

**Q.**The intensity of radiation emitted by the sun has its maximum value at a wavelength 510 nm and that emitted by another star has the maximum value at 350 nm. If we treat them as black bodies, then the ratio of the surface temperature of the sun and the star is

- 0.69
- 1.46
- 1.21
- 0.83

**Q.**The power radiated by a black body is P0, and the wavelength corresponding to maximum energy is λ0. On changing the temperature of black body, it was observed that the power radiated becomes 25681P0. The shift in wavelength corresponding to the maximum energy will be

- λ04
- λ02
- λ0
- 2λ0

**Q.**Distribution of intensity of emitted energy as a function of wavelength is shown in the figure. Point A corresponds to the peak wavelength emitted by a body at certain temperature. Find the correct option when the temperature of the body increases.

- Intensity of A increases, wavelength decreases
- Intensity of A decreases, wavelength decreases
- Intensity of A increases, wavelength increases
- Intensity of A decreases, wavelength increases

**Q.**Mass m of a liquid A is kept in a cup at a temperature of 90∘C. When placed in a room having temperature of 20∘C, it takes 5 min for the temperature of the liquid to drop to 30∘C. Another liquid B having nearly the same density as A and of mass m, kept in another identical cup at 50∘C takes 5 min for its temperature to fall to 30∘C when placed in a room having temperature 20∘C. If the two liquids at 90∘C and 50∘C are mixed in a calorimeter where no heat is allowed to leak, find the final temperature of the mixture. Assume that Newton's law of cooling is applicable for the given temperature ranges.

- 72∘C
- 69.7∘C
- 66∘C
- 52∘C

**Q.**If at temperature T1=1000K, the wavelength is 1.4×10−6m, then at what temperature the wavelength will be 2.8×10−6m

- 2000 K
- 500 K
- 250 K
- None of these

**Q.**Statement 1 : Radiations of longer wavelengths are predominant at lower temperature.

Statement 2 : The wavelength corresponding to maximum emission of radiations shifts from longer wavelength to shorter wavelength as the temperature increases.

- Statement 1 is true, statement 2 is false
- Statement 1 is false, statement 2 is true
- Both Statement 1 and statement 2 are true
- Both Statement 1 and statement 2 are false

**Q.**

Experimental investigations show that the intensity of solar radiation is maximum for a wavelength 480 nm in the visible region. Estimate the surface temperature of the sun. Given Wien's constant, b=2.88× 10−3mK.

5000 K

6000 K

8000 K

106 K

**Q.**Two spherical bodies A (radius 6 cm) and B (radius 18 cm) are at temperatures T1 and T2 , respectively. The maximum intensity in the emission spectrum of A is at 500 nm and in that of B is at 1500 nm. Considering them to be black bodies, what will be the ratio of the rate of total energy radiated by A to that of B ?

**Q.**Solar radiation emitted by sun resembles to that emitted by a black body at a temperature of 6000 K. Maximum intensity is emitted at a wavelength of about 4800 Å. If the sun is cooled down from 6000 K to 3000 K, then the peak intensity would occur at a wavelength of

- 4800 Å
- 9600 Å
- 2400 Å
- 19200 Å