Answer: The layer of air containing ozone gas, located at an altitude of 15-30 km (or 20-50 km according to some sources) within the stratosphere or calm layer, is called the ozone sphere or ozone layer.

Answer: The depletion of the ozone layer located in the stratosphere, at an altitude of 20-30 km from the Earth’s surface, creates a hole known as an “ozone hole.” Scientist Farman identified the depletion of the ozone layer as an ozone hole.

Answer: Due to being highly stable, CFCs released from various sources reach the stratosphere of the atmosphere unchanged. This layer contains ozone (O₃), which absorbs ultraviolet (UV) rays from the Sun and protects us from their harmful effects. That is why it is called the ‘Earth’s umbrella.’ Nowadays, this umbrella is depleting, creating an ‘ozone hole.’ The mechanism of ozone depletion is as follows:
1. Naturally, N₂ and O₂ in the air combine via solar radiation to produce N₂O, which depletes the ozone layer through a photochemical process.
2. However, the main reason is human activity, where CFCs released into the air reach the stratosphere unchanged. CFCs are extremely stable. UV rays from the Sun break down CFCs through free-radical reactions, which then break the ozone layer. These reactions continue in a chain. As a result, a single chlorine free radical destroys thousands of ozone molecules, creating holes in the ozone layer.

Answer: Effect on humans: If UV rays reach the Earth directly, it will cause skin cancer, cataracts, weakened immune systems, respiratory inflammation, bronchitis, and various lung diseases.
Effect on plants and animals: UV rays hinder photosynthesis, reducing food production in plants. It reduces the production of phytoplankton, which in turn reduces the population of fish and other organisms that depend on them.
Effect on climate: The Earth’s temperature will rise, melting polar ice will increase, and sea levels will rise, submerging low-lying areas.

Answer: To prevent ozone depletion, the ‘Montreal Protocol’ international treaty was signed in 1987. According to this treaty:
(i) Stop the production of CFCs and Halons by 1995;
(ii) Phase out CCl₄, CH₃Br, and Methyl chloroform;
(iii) Use hydrocarbons like Isobutane (CH₃)₃CH in CFC aerosols;
(iv) Use Hydro-chlorofluorocarbons (HCFCs) like CHF₂Cl in refrigerators;
(v) Phase out HCFCs and switch to Hydrofluorocarbons (HFCs) by 2040.

Answer: Harmful UV rays are emitted along with solar radiation. The O₃ layer absorbs these UV rays. If UV rays enter the Earth, they can cause skin cancer and weaken the human immune system. Therefore, the O₃ layer protects us by absorbing these harmful UV rays.

Answer: Gases that absorb IR radiation reflected from the Earth’s surface and increase temperature are called greenhouse gases.

Answer: The Earth’s surface is heated by visible light, but it radiates long-wavelength infrared (IR) rays. IR rays cannot penetrate glass. CO₂ and water vapor (H₂O) are polar molecules that absorb IR radiation and increase the temperature. Heat absorbed by CO₂ and water vapor is radiated back to the Earth’s surface, further increasing the temperature. N₂, H₂, and O₂ have no greenhouse effect.

Answer: CO (Carbon Monoxide) is a silent killer because it is a colorless, odorless, and tasteless toxic gas. Humans cannot detect its presence. CO acts as an active ligand and forms a complex compound with iron in the blood’s hemoglobin, blocking oxygen flow in the body.

Answer: Gases like CO₂, CH₄, N₂O, and CFC create the greenhouse effect. The Earth’s surface radiates long-wavelength infrared (IR) rays which are absorbed by these atmospheric gases. This heat is radiated back to the Earth’s surface, increasing the global temperature.

Answer: CO₂ retains more heat than other gases and stays near the Earth’s surface due to its weight. Its concentration is increasing daily, causing the Earth’s temperature to rise. This event is known as the greenhouse effect, hence it is called a greenhouse gas.

Answer: CFCs produce chlorine free radicals that destroy the ozone layer. Through the holes created in the ozone layer, UV rays from the Sun enter the Earth’s atmosphere without obstruction, causing the Earth’s surface temperature to rise. Therefore, CFCs assist in increasing the environmental temperature.

Answer: CO₂ retains a significant portion of reflected heat, preventing it from escaping into space, thus increasing atmospheric temperature. CO₂ and SO₂ react with oxygen and water in the air to produce carbonic acid, sulfurous acid, and sulfuric acid, which cause acid rain. This kills fish in water bodies, prevents crop growth in soil, and causes significant damage to buildings and structures.