According to the provided reference, in a specific experiment using a diffraction grating with 300 lines/mm, the average wavelength of the laser light was measured to be 664.07 nm.
How Diffraction Gratings Measure Wavelength
A diffraction grating is a key optical tool used to measure the wavelength of light with high precision. It consists of a large number of equally spaced parallel slits or lines on a surface. When laser light shines on the grating, it diffracts and interferes, creating bright spots (maxima) at specific angles.
The principle behind this measurement is described by the diffraction grating equation:
d sinθ = nλ
Where:
- d is the distance between adjacent lines (the grating spacing). This is calculated from the number of lines per millimeter or inch. For example, a grating with 300 lines/mm has a spacing d = 1 mm / 300 lines = 1/300 mm.
- θ is the angle between the original direction of the light and the direction of the n-th order bright spot (maximum).
- n is the order of the maximum (n = 0 for the central bright spot, n = 1 for the first bright spots on either side, n = 2 for the second, and so on).
- λ (lambda) is the wavelength of the light.
By measuring the angle θ for a given order n and knowing the grating spacing d, the wavelength λ can be calculated.
Specific Findings from the Reference
The reference provides data from experiments using different diffraction gratings:
| Grating Lines/mm | Order (n) | Measured Wavelength (λ) |
|---|---|---|
| 300 | Average | 664.07 nm |
| 600 | 3 | Unmeasured in this study |
This shows that for the specific laser and experimental setup used with the 300 lines/mm grating, the resulting wavelength was 664.07 nm. The reference also notes that for a 600 lines/mm grating, the wavelength for the 3rd order (n=3) was not measured as part of that particular study.
It's important to note that the wavelength of laser light can vary depending on the type of laser. Red diode lasers, commonly used in laboratory demonstrations, typically emit light with wavelengths in the range of 630 to 670 nm. The 664.07 nm value falls within this typical range for a red laser.
