In Earth atmosphere, the protective ozone layer that absorbs most of the Sun harmful ultraviolet radiation is mainly located in which atmospheric layer?

Introduction / Context:
This question belongs to basic environmental science and geography. The ozone layer plays a vital role in protecting life on Earth by absorbing a large portion of harmful ultraviolet B and ultraviolet C radiation from the Sun. For school level and competitive exams, it is standard to ask in which layer of the atmosphere this ozone concentration is highest. Understanding the structure of the atmosphere is also important for topics like climate, weather, and aviation.

Given Data / Assumptions:

• We are dealing with the Earth atmosphere.
• The focus is on the ozone layer that absorbs harmful ultraviolet radiation.
• We must identify the atmospheric layer where this ozone is most concentrated.
• The common named layers listed are troposphere, stratosphere, ionosphere, mesosphere, and exosphere.

Concept / Approach:
The atmosphere is divided into several layers based on temperature variation with height. Starting from the surface we have the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. The ionosphere is a region within the thermosphere with ionised particles. The ozone layer, often called the ozonosphere, is primarily located in the lower part of the stratosphere, roughly between 15 and 35 kilometres above Earth surface. Therefore, when exams ask where the ozone layer is found, the expected answer is the stratosphere.

Step-by-Step Solution:
Step 1: Recall the basic vertical structure of the atmosphere from ground upwards. Step 2: Remember that the troposphere contains most weather phenomena, but only relatively small amounts of ozone. Step 3: Recall that the maximum concentration of ozone gas occurs in the lower stratosphere, forming the ozone layer. Step 4: Note that the ionosphere is a charged particle region mainly in the thermosphere and not the primary location of ozone. Step 5: Conclude that the correct atmospheric layer is the stratosphere.

Verification / Alternative check:
A quick verification is to connect the word stratosphere with stratospheric ozone, a term often used in climate change discussions. Environmental treaties such as the Montreal Protocol specifically focus on substances that deplete stratospheric ozone. Textbooks consistently show diagrams with the ozone layer in the stratosphere above the troposphere. This matches the answer and confirms that other layers in the options are not correct in this context.

Why Other Options Are Wrong:

• Troposphere: This lowest layer is where clouds and weather occur, but it does not contain the main ozone layer that protects from ultraviolet radiation.
• Ionosphere: A region of ionised particles within the thermosphere, important for radio communication, not the main seat of the ozone layer.
• Mesosphere: Located above the stratosphere and below the thermosphere, known for burning meteors, not for peak ozone concentration.
• Exosphere: The outermost thin layer of the atmosphere, merging into space, and not associated with the protective ozone layer.

Common Pitfalls:
Candidates sometimes confuse the ionosphere with the ozone layer because both lie above the troposphere and both are involved in interactions with solar radiation. Another mistake is to pick the troposphere simply because it is the layer closest to human activity. However, diagrams and standard definitions clearly place the ozone layer in the stratosphere, so careful revision of basic atmospheric structure helps avoid these errors.

Final Answer:
The protective ozone layer is mainly located in the stratosphere, therefore the correct option is Stratosphere.