Monitoring The Atmosphere

Photochemical smog is a type of air pollution that results from the reaction of sunlight with pollutants such as nitrogen oxides (NO_x) and volatile organic compounds (VOCs) in the atmosphere. Here are the essential components:

• Nitrogen Oxides (NO_x): Emitted from vehicle exhausts, power plants, and industrial emissions, NO_x plays a crucial role in the formation of photochemical smog by reacting with VOCs in the presence of sunlight.
• Volatile Organic Compounds (VOCs): These are hydrocarbon compounds that can vaporize into the air. They react with NO_x under sunlight to form ozone, a major component of photochemical smog.
• High Temperature (> 25 degrees): High temperatures accelerate the chemical reactions involved in smog formation. Warmer temperatures increase the evaporation of VOCs and enhance the photochemical reactions producing smog.

The given options for photochemical smog formation include:

• Smoke, water vapour and low temperature (> 25 degrees)
• NO_x, SO₂, and high temperature (> 25 degrees)
• NO_x, VOCs, and high temperature (> 25 degrees)
• Smoke, NO_x, and low temperature (< 25 degrees)

Among these, NO_x, VOCs, and high temperature (> 25 degrees) are the critical factors for photochemical smog formation, making this the correct answer.

The Earth’s atmosphere is divided into several layers, each with distinct properties and temperature gradients. The layers are typically arranged in ascending order from the Earth’s surface as follows:

1. Troposphere: Closest to Earth's surface; weather phenomena occur here.
2. Stratosphere: Above the troposphere; contains the ozone layer.
3. Mesosphere: Above the stratosphere; meteors burn up here.

Additionally, two boundaries separate these layers:

• Stratopause: The boundary between the stratosphere and the mesosphere.
• Mesopause: The boundary marking the top of the mesosphere.

Arranging the given atmospheric layers starting from the Earth's surface:

1. (E) Troposphere
2. (B) Stratosphere
3. (C) Stratopause
4. (A) Mesosphere
5. (D) Mesopause

The correct sequence is: (E), (B), (C), (A), (D).

For electromagnetic radiation, wavelength ranges are generally as follows:

• UV-C: Approximately 100–280 nm (nanometers)
• UV-B: Approximately 280–315 nm
• UV-A: Approximately 315–400 nm
• Infra-red: Approximately 700 nm to 1 mm
• Microwave: Approximately 1 mm to 1 meter

Therefore, arranging these categories by increasing wavelength from shortest to longest gives us: (A) UV-C, (B) UV-B, (C) UV-A, (D) Infra-red, (E) Microwave.

The correct option is: (A), (B), (C), (D), (E).