The main component of photochemical smog is ans. Oxides of nitrogen Sulphur dioxide Water vapour All of the above

The main component of photochemical smog is Oxides of nitrogen.

Photochemical smog, also known as "Los Angeles smog," is a type of air pollution derived from vehicular emission from internal combustion engines and industrial fumes. These pollutants react in the atmosphere with sunlight to form secondary pollutants that also combine with the primary emissions to form photochemical smog.

The formation of photochemical smog involves two major steps:

1. Nitrogen oxides and volatile organic compounds (VOCs) are emitted by cars, power plants, and industrial processes. These pollutants are released into the atmosphere where they react with sunlight to form ozone.

2. The ozone reacts with the nitrogen oxides and VOCs to form more complex compounds, including peroxyacyl nitrates (PANs), aldehydes, and ketones. These compounds make up the majority of photochemical smog.

So, the main component of photochemical smog is not Sulphur dioxide or Water vapour, but Oxides of nitrogen.