Energy Levels: What is the wavelength of the emitted photon if an electron in the hydrogen atom makes a transition from the n = 7 state to the n = 2 state? (c = 3.00 × 108 m/s, h = 6.626 × 10-34 J ? s, 1 eV = 1.60 × 10-19 J)
A. 199 nm
B. 365 nm
C. 4480 nm
D. 398 nm
E. 796 nm
Answer: D
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Compare the four terrestrial world atmospheres
What will be an ideal response?
Hydrogen and oxygen molecules in a sample of gas have the same temperature. This means the hydrogen molecules, on average, have the same
A) speed and the same kinetic energy. B) speed, but more kinetic energy. C) speed, but less kinetic energy. D) kinetic energy, but more speed. E) kinetic energy, but less speed.
The handle of a ladle used for pouring molten lead is 30-cm-long. Originally the handle was made of 1.9 x 1.25 cm mild steel bar stock. To reduce the grip temperature, it is proposed to form the handle of tubing 0.15-cm-thick to the same rectangular shape. If the average heat transfer coefficient over the handle surface is 14 W/(m2 K), estimate the reduction of the temperature at the grip in air at 21°C.
GIVEN
FIND
The reduction of the temperature at the grip
ASSUMPTIONS
The lead is at the melting temperature
The handle is made of 1% carbon steel
The ladle is normally in steady state during use
The variation of the thermal conductivity is negligible
One dimensional conduction
Heat transfer from the end of the handle can be neglected
SKETCH
Air temperature decreases with increasing altitude; this rate of cooling is called the
A) dry adiabatic lapse rate. B) a moist adiabatic rate. C) environmental lapse rate.