Question: what is the difference between normal spectrometer and constant deviation spectrometer?
Answer: To calculate Rydberg's constant, the standard 'prism spectrometer' can also be used. ... (In a 'prism spectrometer', the prism is rigid and the scope can be rotated until the light is brought to focus, whereas in the 'constant deviation' spectrometer, the scope cannot be moved; instead, the prism can be rotated).