1. What is Wavenumber?

Wavenumber (k) is the number of wavelengths per unit distance, typically expressed in reciprocal centimeters (cm⁻¹). It is commonly used in spectroscopy as a unit of frequency.

2. How Does the Conversion Work?

The conversion from wavelength to wavenumber is given by:

Where:

• \( k \) — Wavenumber in cm⁻¹
• \( \lambda_{nm} \) — Wavelength in nanometers (nm)

Explanation: The factor of 10⁷ converts nanometers to centimeters (since 1 cm = 10⁷ nm) and provides the reciprocal relationship between wavelength and wavenumber.

3. Importance of Wavenumber

Details: Wavenumber is directly proportional to energy, making it particularly useful in infrared spectroscopy and Raman spectroscopy where energy transitions are measured.

4. Using the Calculator

Tips: Enter the wavelength in nanometers (nm). The value must be greater than zero. The calculator will provide the corresponding wavenumber in cm⁻¹.

5. Frequently Asked Questions (FAQ)

Q1: Why use wavenumber instead of wavelength?
A: Wavenumber is directly proportional to energy, making spectral features appear equally spaced when plotted against wavenumber.

Q2: What is the range of typical wavenumbers?
A: In infrared spectroscopy, wavenumbers typically range from 4000 cm⁻¹ to 400 cm⁻¹.

Q3: How does this relate to frequency?
A: Wavenumber is proportional to frequency (ν) through the speed of light: \( k = \frac{\nu}{c} \), where c is the speed of light in cm/s.

Q4: Can this be used for all electromagnetic radiation?
A: Yes, the conversion applies to any wavelength, though it's most commonly used for infrared radiation.

Q5: What about other units of wavelength?
A: If your wavelength is in micrometers (μm), multiply by 10⁴ instead of 10⁷ (since 1 cm = 10⁴ μm).