Understanding the Sodium Emission Spectrum

The question asks about the number of emission spectrum lines for sodium that fall within the specific wavelength range of 588 to 590 nanometers (nm). When sodium is heated or excited, it emits light at characteristic wavelengths, forming its emission spectrum.

One of the most prominent features of the sodium emission spectrum is the intense yellow light it produces. This yellow light is actually composed of two very close spectral lines, historically known as the sodium D lines.

These two lines are:

• D₁ line: Approximately 589.6 nm
• D₂ line: Approximately 589.0 nm

Let's check if these wavelengths fall within the given range of 588 nm to 590 nm:

• The D₁ line at 589.6 nm is between 588 nm and 590 nm.
• The D₂ line at 589.0 nm is between 588 nm and 590 nm.

Both of these principal sodium emission lines are located within the specified range of 588 nm - 590 nm. These two lines are often observed together as a doublet, especially at lower resolutions, but they are distinct spectral lines.

Therefore, there are two emission spectrum lines for sodium that lie in the range 588 - 590 nm.