If the wavelengths corresponding to ultraviolet, visible and infrared radiations are given as λ UV ,λ VIS and λ IR respectively, then which one of the following gives the correct relationship among these wavelengths?
λ UV < λ VIS < λ IR
Understanding Wavelengths: Ultraviolet, Visible, and Infrared Radiation
This question asks about the relationship between the wavelengths of three different types of electromagnetic radiation: ultraviolet (UV), visible (VIS), and infrared (IR) radiation. To answer this, we need to understand where these types of radiation fall within the electromagnetic spectrum.
The Electromagnetic Spectrum and Wavelengths
The electromagnetic spectrum is a continuous range of all types of electromagnetic waves, ordered by frequency and wavelength. Different parts of the spectrum are given different names based on their characteristics and how they interact with matter.
The order of electromagnetic radiation types from longest wavelength to shortest wavelength is generally:
- Radio waves
- Microwaves
- Infrared radiation (IR)
- Visible light (VIS)
- Ultraviolet radiation (UV)
- X-rays
- Gamma rays
Wavelength (\(\lambda\)) and frequency (\(f\)) are inversely related for electromagnetic waves traveling in a vacuum or the same medium, according to the equation \(c = \lambda f\), where \(c\) is the speed of light. This means that as wavelength increases, frequency decreases, and vice versa.
Comparing UV, Visible, and Infrared Wavelengths
Based on the order in the electromagnetic spectrum:
- Infrared radiation (IR) is next to visible light on the side of longer wavelengths.
- Visible light (VIS) occupies a range of wavelengths that our eyes can detect (the colors of the rainbow, from red to violet). Red light has the longest wavelength within the visible spectrum, and violet light has the shortest.
- Ultraviolet radiation (UV) is next to visible light on the side of shorter wavelengths (beyond violet).
Therefore, comparing these three:
- Infrared radiation has longer wavelengths than visible light.
- Ultraviolet radiation has shorter wavelengths than visible light.
This gives us a clear order for the wavelengths:
Wavelength of Ultraviolet (\(\lambda_{UV}\)) < Wavelength of Visible (\(\lambda_{VIS}\)) < Wavelength of Infrared (\(\lambda_{IR}\))
Analyzing the Options
Let's look at the given options and compare them to our finding:
- Option 1: \(\lambda_{UV} < \lambda_{IR} < \lambda_{VIS}\) (Incorrect, states IR is shorter wavelength than Visible)
- Option 2: \(\lambda_{UV} > \lambda_{VIS} > \lambda_{IR}\) (Incorrect, states UV is longer wavelength than Visible and Visible is longer than IR)
- Option 3: \(\lambda_{UV} > \lambda_{IR} > \lambda_{VIS}\) (Incorrect, states UV is longest and Visible is shortest among the three)
- Option 4: \(\lambda_{UV} < \lambda_{VIS} < \lambda_{IR}\) (Correct, states UV is shortest, Visible is in the middle, and IR is longest)
The relationship \(\lambda_{UV} < \lambda_{VIS} < \lambda_{IR}\) correctly represents the relative wavelengths of ultraviolet, visible, and infrared radiation.
| Radiation Type | Approximate Wavelength Range | Relative Wavelength |
|---|---|---|
| Ultraviolet (UV) | 10 nm to 400 nm | Shortest among the three |
| Visible (VIS) | 400 nm to 700 nm | Middle range |
| Infrared (IR) | 700 nm to 1 mm | Longest among the three |
From the table and the position in the electromagnetic spectrum, it is clear that the wavelength order is Ultraviolet < Visible < Infrared.
Conclusion
The correct relationship between the wavelengths of ultraviolet (\(\lambda_{UV}\)), visible (\(\lambda_{VIS}\)), and infrared (\(\lambda_{IR}\)) radiation is \(\lambda_{UV} < \lambda_{VIS} < \lambda_{IR}\).
Revision Table: Key Concepts on Electromagnetic Spectrum
| Concept | Description | Relationship with Wavelength |
|---|---|---|
| Electromagnetic Spectrum | The range of all possible frequencies of electromagnetic radiation. | Ordered by wavelength and frequency. |
| Wavelength (\(\lambda\)) | The distance between successive crests or troughs of a wave. | Inversely proportional to frequency (\(f\)) in a given medium (\(c = \lambda f\)). |
| Frequency (\(f\)) | The number of wave cycles passing a point per unit time. | Inversely proportional to wavelength (\(\lambda\)). Higher frequency means shorter wavelength. |
| Energy | Related to frequency (\(E = hf\)). Higher frequency means higher energy. | Inversely related to wavelength (\(E = hc/\lambda\)). Shorter wavelength means higher energy. |
Additional Information: Properties of UV, Visible, and IR Radiation
Understanding the properties of these radiation types is important:
- Visible Light: This is the portion of the spectrum detectable by the human eye, ranging from violet (shortest wavelength, highest frequency) to red (longest wavelength, lowest frequency). It is crucial for vision and plays a role in processes like photosynthesis.
- Ultraviolet (UV) Radiation: Found just beyond the violet end of the visible spectrum, UV radiation has shorter wavelengths and higher energy than visible light. It can cause sunburn and skin damage but is also used in sterilization and forensics. The sun is a major source of UV radiation.
- Infrared (IR) Radiation: Located just beyond the red end of the visible spectrum, IR radiation has longer wavelengths and lower energy than visible light. It is often associated with heat and is used in thermal imaging, remote controls, and heating systems. All objects with a temperature above absolute zero emit IR radiation.
The difference in wavelengths (and thus frequencies and energies) is what gives each type of radiation its unique properties and applications.
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