Question

Indicate the region of the spectrum for each of the following wavelengths of light. (a) \(280 \mathrm{nm}\) (b) \(1200 \mathrm{nm}\)

Short answer

280 nm is in the UV region; 1200 nm is in the IR region.

Step-by-step solution

Understanding Wavelengths and Spectrums

Light waves are characterized by their wavelengths, and different regions of the electromagnetic spectrum correspond to different wavelength ranges. The ultraviolet (UV) spectrum is typically from about 10 nm to 400 nm, the visible spectrum is from about 400 nm to 700 nm, and the infrared (IR) spectrum is from about 700 nm to 1 mm (1,000,000 nm).

Analyzing Wavelength 280 nm

Given that 280 nm is significantly smaller than the lower limit of the visible spectrum (400 nm) and falls within the limit of the UV spectrum (10 nm to 400 nm), it can be concluded that this wavelength belongs to the ultraviolet (UV) region.

Analyzing Wavelength 1200 nm

The wavelength 1200 nm is larger than the upper limit of the visible spectrum (700 nm) but falls within the infrared spectrum range (700 nm to 1 mm). Hence, it belongs to the infrared (IR) region.

Key concepts

Ultraviolet Spectrum

The ultraviolet (UV) spectrum is a fascinating region of the electromagnetic spectrum. It lies beyond the visible light that our eyes can perceive. Ultraviolet radiation has shorter wavelengths than visible light, typically ranging from about 10 nm to 400 nm.

• **Short-Wave UV (UVC)**: This ranges from 100 nm to 280 nm. It is the most energetic form, capable of causing chemical reactions and even sterilizing equipment.
• **Mid-Wave UV (UVB)**: Spanning from 280 nm to 320 nm, UVB rays are responsible for causing sunburn and can be harmful in large doses.
• **Long-Wave UV (UVA)**: Ranges from 320 nm to 400 nm. UVA rays penetrate the Earth’s atmosphere and are responsible for skin aging and tanning.

Understanding UV radiation is important because it plays a significant role in processes like vitamin D production in our skin but can also lead to health issues like skin cancer with excessive exposure.
In the exercise mentioned above, the 280 nm wavelength falls into the UV spectrum, specifically within the UVB range.

Infrared Spectrum

Infrared (IR) radiation is a type of electromagnetic radiation with wavelengths longer than visible light but shorter than radio waves. It spans a range from 700 nm to 1 mm.
This spectrum is crucial for various technologies, including night-vision devices and thermal imaging.

• **Near-Infrared (NIR)**: Ranges from about 700 nm to 1400 nm. This is the region closest to visible light, and it is often used in fiber optic communications.
• **Mid-Infrared (MIR)**: From 1400 nm to 3000 nm. This range is useful in various chemical analysis techniques due to its ability to excite molecular vibrations.
• **Far-Infrared (FIR)**: Stretches from 3000 nm to 1 mm. Far-infrared is largely used in thermal imaging to detect heat emitted by objects.

As per the exercise, a wavelength of 1200 nm places it in the near-infrared region. Devices such as remote controls often utilize this part of the spectrum.

Wavelength Analysis

When analyzing electromagnetic waves, understanding the concept of wavelength is fundamental. Wavelength is the length of one wave cycle, commonly measured in nanometers (nm) for light waves.
It determines the type of electromagnetic radiation it is, ranging across various spectra from gamma rays to radio waves.
Accuracy in wavelength analysis allows scientists and engineers to categorize the type of radiation and predict its interactions with matter and energy.

• **Shorter Wavelengths**: These, like ultraviolet, carry more energy and can penetrate materials more deeply than others.
• **Longer Wavelengths**: Such as those in the infrared spectrum, have lower energy but are perfect for everyday technology applications like thermal cameras.

In practice, determining which part of the electromagnetic spectrum a given wavelength belongs to is essential in fields ranging from astronomy to medical diagnostics and telecommunications. The step-by-step solution for the wavelengths of 280 nm and 1200 nm highlights this analysis approach, categorizing them as UV and IR respectively.