Animated Solution for Chemistry - Environmental Chemistry: The upper stratosphere consisting of the ozone layer protects us from the sun's radiation that falls in the wavelength region of

Imagine looking up at the sky on a bright, sunny day. High above the weather, the clouds, and the airplanes, in a region called the stratosphere (about $10\text{ km}$ to $50\text{ km}$ above sea level), lies an invisible, life-saving shield. This is the ozone layer.

Without this layer, life on Earth as we know it would be impossible. But what exactly is it protecting us from? The sun is a massive nuclear reactor, emitting a wide spectrum of electromagnetic radiation. While the visible light safely reaches the surface to illuminate our world, the sun also hurls highly energetic, invisible rays towards us.

The ozone layer acts as a cosmic bouncer. It allows the relatively harmless visible light to pass through but aggressively absorbs harmful Ultraviolet (UV) radiation.

To understand this mathematically, we need to look at the electromagnetic spectrum. Visible light falls between $400\text{ nm}$ and $700\text{ nm}$. UV radiation has shorter wavelengths, ranging from $1\text{ nm}$ to $400\text{ nm}$. In physics, a shorter wavelength means higher frequency and, consequently, higher energy ($E=\frac{hc}{\lambda }$). This high energy is what makes UV rays capable of breaking chemical bonds and damaging our DNA.

Let's evaluate the options provided in the question based on our knowledge of the electromagnetic spectrum:

(a) $600-750\text{ nm}$: This range falls squarely in the visible (orange/red) and near-infrared regions. (b) $400-550\text{ nm}$: This is also in the visible spectrum (violet to green). (c) $0.8-1.5\text{ nm}$: These extremely short wavelengths belong to the highly penetrating X-ray region. (d) $200-315\text{ nm}$: This range sits perfectly inside the Ultraviolet (UV) region.

Therefore, the ozone layer protects us from radiation in the $200\text{ nm}$ to $315\text{ nm}$ range.

The Types of UV

It is fascinating to note that UV radiation is further divided into three categories based on wavelength:

1. UV-A ($315-400\text{ nm}$): The least energetic. It mostly passes through the ozone layer and is responsible for skin aging. 2. UV-B ($280-315\text{ nm}$): Highly energetic and causes sunburns. The ozone layer absorbs the vast majority of it. 3. UV-C ($100-280\text{ nm}$): The most dangerous and lethal form of UV. Thankfully, it is completely absorbed by oxygen and ozone in the upper atmosphere.

Our correct option, $200-315\text{ nm}$, perfectly encapsulates the dangerous UV-B and UV-C rays that the ozone layer so graciously filters out for us!