The ozone layer which is responsible for protecting life on earth from harmful UV radiation from the Sun is located in which layer of the atmosphere?

Stratosphere

The correct answer is Option (3) → Stratosphere

The ozone layer is located in the stratosphere, specifically in the lower to middle part of this atmospheric layer (roughly between 15–35 km above Earth's surface).

Here’s why the others are incorrect:

• Troposphere — The lowest layer (0–10/15 km), where weather occurs and most clouds form. It contains only a very small amount of ozone.
• Ionosphere — A region within the upper atmosphere (overlapping parts of the mesosphere and thermosphere, ~50–1000 km). It is ionized by solar radiation and affects radio waves, but does not contain the main ozone layer.
• Mesosphere — The layer above the stratosphere (~50–85 km). It is very cold and has very little ozone.

The high concentration of ozone (O₃) in the stratosphere absorbs most of the Sun’s harmful ultraviolet (UV) radiation (especially UVB and UVC), protecting life on Earth from skin cancer, cataracts, and damage to ecosystems.

So, the ozone layer is in the Stratosphere.