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【单选题】
Two main factors are necessary to create a stable foam , they are ( ):A.
van der Waals force
B.
a repulsive force between the two film surfaces across the water film;
C.
a mechanism to induce surface elasticity in the film to protect against mechanical disturbances.
D.
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【判断题】Business is the human activity related to material things and can be found in all societies.
A.
正确
B.
错误
【单选题】The wavelength of an electron with kinetic energy, 50 eV is ( ).
A.
1.7 nm
B.
3.4 nm
C.
0.34 nm
D.
0.17 nm
【简答题】(a) What is the wavelength of an X-ray photon of energy 10.0 keV? (b) What is the wavelength of a gamma-ray photon of energy 1.00 MeV? (c) What is the range of energies of photons of visible light wit...
【单选题】根据物质流动是否主要由人类活动引起可分成（ ）两类The material flow can be divided into the following（ ）two categories according to whether the material flow is mainly caused by human activity
A.
物质生物地球化学流动和人为流动 Material biogeochemical flow and its anthropogenic cycle
B.
物质随大气流动和随水体流动 Material flowing with the atmosphere and with the water body
C.
物质工业流动和农业流动 Material industrial and agricultural flows
D.
物质产业流动和消费流动 Material industry flow and consumption flow
【单选题】The wavelength of an EM wave is 0.44 μm, then what is its frequency?
A.
6.82e10 Hz
B.
0.15e(-14) Hz
C.
6.82e5 GHz
D.
1.32e2 Hz
【单选题】Due to factors like geographic position, atmospheric circulation, _______ and human activity, China can be divided into three climate zones.
A.
temperature
B.
altitude
C.
longitude
D.
precipitation
【单选题】The wavelength of an electron whose velocity is 1.7 × 10 4 m/s and whose mass is 9.1 × 10 -28 g is __________ m.
A.
4.3 × 10 -11
B.
12
C.
4.3 × 10 -8
D.
2.3 × 10 7
E.
2.3 × 10 -7
【简答题】what the wavelength of an electromagnetic wave required to image an object?
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