Question

What is the detector in a spectrograph in which spectral lines are recorded photographically?

Short answer

The detector used in the spectrograph is photographic film.

Step-by-step solution

Step 1. Given information

The detector in a spectrograph should be determined.

Step 2. Define spectrograph

The spectrograph is a light-tight box with a narrow aperture that allows light to enter, a grating that breaks the light into small components, and a detector that records the light spectrum at a distance from the grating.

Step 3. Determining the detector in a spectrograph 

Since wavelengths vary, the principal role of a detector in a spectrograph is to perceive and measure incoming light radiation across a variety of wavelengths. Photographic film or an electronic detector are the most popular types of detectors used in spectrographs to record the spectrum for examination. The spectrum captured by these plates is traced with a device called a microdensitometer. The graph of light intensity in terms of wavelength will be represented by the resulting spectrum traced.