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Morgarella [4.7K]
3 years ago
6

What did the greeks call the mineral they found and why?

Physics
1 answer:
Elza [17]3 years ago
6 0
Ancient civilizations had a high demand for raw materials, like clay, diverse rocks and, most of all, metals. These were required for buildings, crafts, agriculture, their armed forces, financial concerns, art and culture. Clays and rocks produced by opencast mining primarily served for the production of bricks and building blocks, which were used for civil and hydraulic engineering.
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1. Astronomical observatories have been available since ancient times, and many cultures set aside special sites for astronomica
nydimaria [60]

Answer:

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Explanation:

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The map here shows land surface temperatures on earth during one month in 2015
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Read 2 more answers
Ultraviolet light of wavelength 270 nm strikes a metal whose work function is 2.3 eV.What is the shortest de Broglie wavelength
soldier1979 [14.2K]

Answer:

The shortest de Broglie wavelength for the electrons that are produced as photoelectrons is 0.81 nm

Explanation:

Given;

wavelength of ultraviolet light, λ = 270 nm

work function of the metal, φ = 2.3 eV = 2.3 x 1.602 x 10⁻¹⁹ J = 3.685 x 10⁻¹⁹ J

The energy of the ultraviolet light is given by;

E = \frac{hc}{\lambda}\\\\E = \frac{(6.626*10^{-34} )(3*10^{8}) }{270*10^{-9} }\\\\E = 7.362 * 10^{-19} \ J

The energy of the incident light is related to kinetic energy of the electron and work function of the metal by the following equation;

E = φ  + K.E

K.E = E - φ

K.E = (7.362 x 10⁻¹⁹ J) - (3.685 x 10⁻¹⁹ J )

K.E = 3.677 x 10⁻¹⁹ J

K.E = ¹/₂mv²

mv² = 2K.E

velocity of the electron is given by;

V = \sqrt{\frac{2K.E}{m} }\\\\V =  \sqrt{\frac{2(3.677*10^{-19}) }{9.1*10^{-31} } }\\\\V = 8.99*10^{5}  \ m/s

the shortest de Broglie wavelength for the electrons is given by;

\lambda = \frac{h}{mv}\\ \\\lambda = \frac{6.626*10^{-34} }{(9.1*10^{-31})( 8.99*10^{5} )}\\\\\lambda = 8.10*10^{-10} \ m\\\\\lambda = 0.81 \ nm

Therefore, the shortest de Broglie wavelength for the electrons that are produced as photoelectrons is 0.81 nm

7 0
3 years ago
What does it mean if the moon is waxing and waning
konstantin123 [22]
Both verbs come from Olde English. 
That's why everybody clearly understood their meaning until
a hundred years ago, but nobody understands them now.


"Waxing"  =  growing

For two weeks after the New Moon, it's growing toward Full.
First it's a waxing crescent for a week, then it's waxing gibbous.


"Waning"  =  shrinking

For two weeks after the Full Moon, it's shrinking toward New.
First it's waning gibbous for a week, then it's a waning crescent.
6 0
3 years ago
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