An important reaction in the formation of photochemical smog is the photodissociation of NO : NO2 + hv → NO(g) + O(g) The maximum wavelength of light that can cause this reac- tion is 420 nm. (a) In what part of the electromagnetic spec- trum is light with this wavelength found?

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1. 1. The electromagnetic spectrum is divided into several regions based on the wavelength of the radiation. These regions include radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
2. 2. The wavelength of light is usually measured in nanometers (nm). The visible light region of the electromagnetic spectrum ranges from about 400 nm to 700 nm.
3. 3. The given wavelength for the photodissociation of NO is 420 nm. This falls within the range of the visible light region.
4. 4. More specifically, within the visible light region, different colors correspond to different wavelengths. Violet light has the shortest wavelength (around 400 nm), and red light has the longest wavelength (around 700 nm).
5. 5. Therefore, light with a wavelength of 420 nm is found in the visible light region of the electromagnetic spectrum, and it corresponds to the color violet.

Key Concepts

Electromagnetic Spectrum

The electromagnetic spectrum encompasses all types of electromagnetic radiation, arranged by wavelength or frequency. It includes gamma rays, X-rays, ultraviolet light, visible light, infrared radiation, microwaves, and radio waves. The visible spectrum, which is the portion detectable by the human eye, ranges from approximately 400 nm (violet) to 700 nm (red). Understanding where a specific wavelength falls within this spectrum is crucial for identifying its properties and effects.

Photodissociation

Photodissociation is a chemical process in which a molecule absorbs light energy and breaks down into smaller components, often resulting in the formation of free radicals. In the context of the given reaction, the absorption of light by nitrogen dioxide (NO2) leads to its dissociation into nitric oxide (NO) and an oxygen atom (O). This process is significant in atmospheric chemistry, particularly in the formation of pollutants like photochemical smog.

Wavelength and Energy Relationship

The energy of electromagnetic radiation is inversely related to its wavelength, described by the equation E = hc/λ, where E is energy, h is Planck's constant, c is the speed of light, and λ is the wavelength. Shorter wavelengths correspond to higher energy photons, while longer wavelengths have lower energy. This relationship is essential for understanding which wavelengths can initiate specific chemical reactions, such as the photodissociation of NO2 at 420 nm.