Chemistry
The lustre of the metals is because of

High density, due to closed packing of atoms
Reflection of light due to the presence of free electrons
High polish
Absorption of light due to the presence of cavities

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Chemistry
Photo chemical smog is a resultant of the reaction among

CO, O2 and peroxy acetyl nitrate in the presence of Sunlight
CO, CO2 and NO2at low temperature
High concentration of NO2, O3, and CO in the evening
NO2, O3 and peroxy acetyl nitrate in the presence of Sunlight

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