30 Questions
What is used to express the time of day in solar energy calculations?
Apparent Solar Time (AST)
What is the time when the sun crosses the meridian of the observer called?
Local Solar Noon
What factor causes the Equation of Time (ET) variation throughout the year?
Earth's orbital eccentricity
Why does Apparent Solar Time (AST) differ slightly from mean time kept by a clock?
Because of Earth's orbital velocity variations
What must be used to convert Local Standard Time (LST) to Apparent Solar Time (AST)?
Longitude correction
Which factor contributes to the non-uniform length of a day throughout the year?
Earth's axial tilt
What is the significance of the plus sign in Eq (2.4) when calculating the sun-earth distance?
Indicates the sun-earth distance at aphelion position
How is the mean sun-earth distance, 'a', defined?
Half the sum of perihelion and aphelion distances
What is the approximate percentage difference between the longest and shortest sun-earth distances?
3.3%
In which season is the sun higher in the sky according to common knowledge?
Summer
How often does the earth move around the sun in an elliptical orbit?
Yearly
What does the equation R = a(1 - e) represent?
Sun-earth distance at perihelion
What is the name of the equation derived by Max Planck to describe the monochromatic emissive power of a blackbody?
Planck's equation for blackbody radiation
What does the constant C1 represent in Planck's equation for blackbody radiation?
Constant related to radiation intensity
How is the equation (2.34) modified when the surface is not in a vacuum or a gas?
By replacing C1 with C1/n^2
What type of surfaces are often considered as diffuse reflectors in engineering calculations?
Rough surfaces
What does Wien's displacement law provide?
The wavelength corresponding to the maximum of the distribution for blackbody radiation
A real surface is both a diffuse emitter and a diffuse reflector. What does this imply about the radiosity of the surface?
It remains constant in all directions
Which constant is used to calculate C2 in Planck's equation for blackbody radiation?
Boltzmann’s constant
What is the equation used for a real surface to calculate the intensity of radiation from it?
$J = 2.43 \times I$
What does C2 represent in Planck's equation for blackbody radiation?
Constant related to temperature
In Example 2.10, what is the transmissivity of the glass used in the application for wavelengths 0.3 and 3.0 mm?
0.92
What percentage of incident solar energy is transmitted through the glass for wavelengths between 0.3 and 3.0 mm?
94.61%
Based on the provided text, what is the primary assumption made about the interior of the application mentioned in Example 2.10?
It is a blackbody at 373 K
What is the total emissive power of the surface when the average emissive power over the entire wavelength is given as 0.4432?
25129.4 W/m2
At a temperature of 2500 K, what is the computed value of Eb for the given surface?
0.63371 sT^4
What is the average absorptivity of the surface when the spectral absorptivity values are 0.2 and 0.7 for different wavelengths?
0.383
Based on the Kirchhoff's law, if a(T) = 0.383, what is the reflectivity (r) of the surface?
0.617
At a temperature of 2500 K, what is the computed value of ε(T) based on Eq.(2.41) and the provided average absorptivity value?
0.383
What law is used to obtain other properties of materials as demonstrated in Example 2.12?
Kirchhoff’s law Eq.(2.40)
Learn about Max Planck's derivation of the functional relation for monochromatic emissive power of a blackbody using quantum theory. Understand the components and significance of Planck's equation for blackbody radiation.
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