(b) What is the energy density of the Sun's radiation?
A.
B.
C.
D.
JU-PHY2nd YearFinalThermal PhysicsRadiationStefan-Boltzmann law; Wien's displacement law. (Topic Practice)JU-PHY - ⚡ অনলাইন প্রশ্নব্যাংক দেখুন 💥
Another Explanation (5):
The energy density of the Sun's radiation at 1 AU (Earth's average distance from the Sun) is approximately 1.36 kW/m2 (also known as the solar constant).
Related Questions (Any University/Year)
- (b) State and explain Stefan-Boltzmann's law.
- (g) A black sphere of diameter 4 cm is heated to 400 K when the surrounding temperature is 300 K. What is the rate at which energy is radiated? Given \( \sigma = 6 \times 10^{-8} \, \text{Wm}^{-2} \, \text{K}^{-4} \).
- (b) State Kirchhoff's law. From Stefan's law derive Newton's law of cooling. [6]
- (d) If a black body at temperature \(6174 \, \text{K}\) emits \(4700 \, \text{Å}\) with maximum energy. Calculate the temperature at which it emits a wavelength of \(1.4 \times 10^{-3} \, \text{m}\) with maximum energy.
- (d) An aluminum foil of relative emittance 0.1 is placed in between two concentric spheres at temperatures 300 K and 200 K respectively. Calculate the temperature of the foil after the steady state is reached. Assume that the spheres are perfect blackbody radiators. Also calculate the rate of energy transfer between one of the spheres and the foil. [\(\sigma = 5.672 \times 10^{-8} \, \text{M.K.S. units}\)]
- b) Derive Wien's law of energy distribution.
- (c) A black body at temperature 4980 K emits radiation of wavelength 4000 Å with maximum energy. Calculate the temperature at which it will emit a wavelength of \(1.45 \times 10^{-5} \, \text{cm}\) with maximum energy.
- (c) What is the wavelength of maximum intensity radiation radiated from a source at temperature \(3000^\circ \text{C}\)? (Wien's constant \(b = 0.288 \, \text{cm} \cdot \text{K}\)).
- (d) Calculate the maximum amount of heat which may be lost per second by radiation from a sphere of 5 cm in diameter at a temperature of 600 K when is placed in an encloser at a temperature of 300 K. Given that \(\sigma = 5.7 \times 10^{-12} \, \text{watts/cm}^{-2} / (\circ C)^{-4}\).
- (f) Calculate the surface temperature of sun and moon given that \( \lambda_m = 4753 \text{\AA} \) and \( 14 \mu \text{m} \) respectively, \( \lambda_m \) being wavelength of maximum intensity of emission.
- (h) Calculate the energy radiated per minute from the filament of an incandescent Lamp at 1500 K if the surface area is \(4.5 \times 10^{-5} \, \text{m}^2\) and its relative emittance is \(0.65 \, (\sigma = 5.672 \times 10^{-8} \, \text{W/m}^2\text{K}^4)\).
- f) If a blackbody at temperature 6174 K emits 4700 Å with maximum energy, calculate the temperature at which it will emit a wavelength of \(1.4 \times 10^{-3}\) m with maximum energy.
- (4) The spectral energy curve of sunlight has a maximum at a wavelength of \(4.84 \times 10^{-7} \, \text{m}\). Assuming the Sun to be a black body,
- (a) What is the temperature of its emitting surface?
- (c)Calculate the surface temperature of sun and moon given that \( \lambda_m = 4753 \, \text{Å} \) and 14 \(\mu \text{m}\) respectively, \( \lambda_m \) being wavelength at the maximum intensity of emission.
- (xiii) State Stefan-Boltzmann law.
- (d) Calculate the maximum amount of heat which may be lost per second by radiation from a sphere of 5 cm in diameter at a temperature of 600 K when placed in an enclosure at a temperature of 300 K. Given that, \(\sigma = 5.7 \times 10^{-12} \, \text{watts/cm}^{-2}/(^\circ \text{C})^{-1}\).
- (j) State Wien’s displacement law.
- (5) Two large closely spaced concentric spheres (both are black body radiators) are maintained at temperatures of 200 K and 300 K respectively. The space in between the two spheres is evacuated. Calculate the net rate of energy transfer between the two spheres. [Given: \(\sigma = 5.672 \times 10^{-8} \, \text{W/m}^2\text{K}^4\)]
- (g) If a black body at temperature 6174 K emits 4700 \text{\AA} with maximum energy; Calculate the temperature at which it will emit a wavelength of \( 1.4 \times 10^{-5} \text{m} \) with maximum energy.