Q. No.Radiation energy corresponding to the temperature \(T\) of the sun is \(E.\) If its temperature is doubled, then its radiation energy will be:
1. \(32 E\)
2. \(16 E\)
3. \(8 E\)
4. \(4 E\)
1. \(32 E\)
2. \(16 E\)
3. \(8 E\)
4. \(4 E\)
A sphere maintained at a temperature of 600 K, has a cooling rate R in an external environment of 200 K temperature. If its temperature falls to 400 K, then its cooling rate will be:
1.
2.
3.
4. None
If \(\lambda_m\) denotes the wavelength at which the radioactive emission from a black body at a temperature \(T\) K is maximum, then:
1. \(\lambda_m\) is independent of \(T\)
2. \(\lambda_m \propto T\)
3. \(\lambda_m \propto T^{-1}\)
4. \(\lambda_m \propto T^{-4}\)
Two conducting slabs of heat conductivity \(K_{1} ~\text{and}~K_{2}\) are joined as shown in figure. If the temperature at the ends of the slabs are \(\theta_{1}~\text{and}~\theta_{2} \ (\theta_{1} > \theta_{2} ), \) then the final temperature \( \left(\theta\right)_{m} \) of the junction will be:
| 1. | \(\frac{K_{1} \theta_{1} + K_{2} \theta_{2}}{K_{1} + K_{2}}\) | 2. | \(\frac{K_{1} \theta_{2} + K_{2} \theta_{1}}{K_{1} + K_{2}}\) |
| 3. | \(\frac{K_{1} \theta_{2} + K_{2} \theta_{1}}{K_{1} - K_{2}}\) | 4. | None |
Wien's displacement law expresses the relation between:
| 1. | Wavelength corresponding to maximum energy and temperature |
| 2. | Radiation energy and wavelength |
| 3. | Temperature and wavelength |
| 4. | Colour of light and temperature |
Which of the following is closest to an ideal black body?
| 1. | Black lamp |
| 2. | Cavity maintained at a constant temperature |
| 3. | Platinum black |
| 4. | A lump of charcoal heated to high temperature |
For a black body at a temperature of 727ºC, its radiating power is 60 watts and the temperature of the surroundings is 227ºC. If the temperature of the black body is changed to 1227ºC then its radiating power will be:
1. 304 W
2. 320 W
3. 240 W
4. 120 W
Consider two rods of the same length and different specific heats \((S_1,S_2)\) conductivities \((K_1,K_2)\) and area of cross-sections \((A_1,A_2)\) and both having temperature \(T_1\) and \(T_2\) at their ends. If the rate of loss of heat due to conduction is equal, then:
1. \(K_1A_1=K_2A_2\)
2. \(\frac{K_1A_1}{S_1}=\frac{K_2A_2}{S_2}\)
3. \(K_2A_1=K_1A_2\)
4. \(\frac{K_2A_1}{S_2}=\frac{K_1A_2}{S_1}\)
A black body has a wavelength \(\lambda_m\) corresponding to maximum energy at \(2000~\text{K}\). Its wavelength corresponding to maximum energy at \(3000~\text{K}\) will be:
| 1. | \(\dfrac{3}{2}\lambda_m\) | 2. | \(\dfrac{2}{3}\lambda_m\) |
| 3. | \(\dfrac{16}{81}\lambda_m\) | 4. | \(\dfrac{81}{16}\lambda_m\) |
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