Solar Constant and Important Notes

Solar constant (s)

• Solar energy incident on unit area in unit time normally.
• Its value is 1400 $\frac{w}{m^2}$ for surface of earth
• $\therefore S=\sigma (\frac{R^2}{r^2})T^4$
• Where R=Radius of sun, r= Distance of earth from sun, T=Temperature of sun

useful information:

• Mercury though a liquid is heated by conduction and not by convection.
• It is the opening that acts as a black body in Ferry`s Black body.
• In a dark room a hot black body shines more than others.
• Radiation emitted from a perfectly black body does not depend on the nature of its material.
• Radiation is the fastest way of heat transfer.
• When a green glass is heated to high temperature it will glow with the red light.
• Birds often swell their feathers in winter because the air enclosed inside feather is bad conductor of heat.
• We cannot boil water inside an earth satellite by convection.
• Two thin blankets are warmer than a single blanket of double the thickness. (air trap inside the double blanket is bad conductor of heat)