Which of the following did the planetary model of the atom fail to explain?
A. the relationship between orbital radius and energy
B. why alpha particles in Rutherford’s experiment deflected at high angles when incident on atomic foils
C. why most alpha particles in Rutherford’s experiment passed with little deflection through atomic foils
D. why electrons in atoms don’t radiate all their energy away rapidly
D. why electrons in atoms don’t radiate all their energy away rapidly
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For what slit separation will no 1st order double-slit-fringe appear for 550. nm light?
What will be an ideal response?
Cooled air is flowing through a long sheet metal air conditioning duct, 0.2 m high and 0.3 m wide. If the duct temperature is 10°C and passes through a crawl space under a house at 30°C, estimate
(a) The heat transfer rate to the cooled air per meter length of duct.
(b) The additional air conditioning load if the duct is 20-m-long.
(c) Discuss qualitatively the energy conservation if the duct were insulated with glass
wool.
GIVEN
• An air conditioning duct in a crawl space
• Duct height (H) = 0.2 m
• Duct width (w) = 0.3 m
• Duct temperature (Ts) = 10°C
• Ambient temperature (T?) = 30°C
FIND
(a) The heat transfer rate per meter length (qc/L) to the cooled air in the duct
(b) The additional air conditioning load (q20) if the duct length (L) = 20 m
(c) Discuss qualitatively the energy conservation if the duct were insulated with glass wool
ASSUMPTIONS
• Ambient air is still
• Duct temperature is constant and uniform
• Radiation is negligible
• Edge effects are negligible
• No condensation on the duct surface
SKETCH
PROPERTIES AND CONSTANTS
for dry air at the mean temperature of 20°C
Thermal expansion coefficient (?) = 0.00341 1/K
Thermal conductivity (k) = 0.0251 W/(m K)
Kinematic viscosity (?) = 15.7 × 10–6 m2/s
Prandtl number (Pr) = 0.71
A zoom lens is adjusted to change its focal length from 38 mm to 304 mm. If the same amount of light is to be admitted to the lens, what is the final f-number if the original f-number was 2.0?
What will be an ideal response?
The bond energy for a hydrogen molecule is
A) 1.5 eV. B) 2.5 eV. C) 3.5 eV. D) 4.5 eV. E) 5.5 eV.