Which of the following radiations has the longest wavelength?
a. Infrared
b. Visible
c. Ultraviolet
d. X-rays
a
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In the open ocean, the tides are waves that have a period of 12 hours and a speed of 750 km/hr. What is their wavelength?
What will be an ideal response?
Nomads in the desert make ice by exposing a thin water layer to cold air during the night. The icing or freezing of thin layers of water is often also referred to as ice making by nocturnal ( or night time ) cooling, where the surface temperature of water is lowered considerably by radioactive and convective cooling, and it had been practiced extensively in ancient India. To model this process and evaluate the conduction process in water layer, consider a 5-mm thick horizontal layer gets cooled such that its top surface is at temperature of - 5 0C. After a while the water begins to freeze at top surface and the ice front expands downwards through the water layer. Determine the location of solid liquid(ice-water) interface if the bottom surface temperature of the liquid water is at 30C.
State your assumptions for the model and calculations.
GIVEN
• Thickness of the layer(t)= 5 mm
• Surface temperature (Ts)= -50C=268 K
• Water temperature(Tw)= 30C= 276 K FIND
Location of solid liquid interface .
ASSUMPTIONS
• 1 Dimensional steady state heat transfer
• Constant properties throughout time
• Negligible radiation
• Negligible convection by liquid.
SKETCH
The overall direction of change in the universe is toward
A. a state of increased mass in the universe. B. a state of greater disorder. C. a state of increased organization. D. increased energy content of the universe.
Hydrogen is generally classified as a
a. semimetal. b. nonmetal. c. metal. d. noble gas.