Stray light is tested using which instrument component?

• A. Sharp cutoff filters
• B. Didymium glass
• C. Filters and a solution with no absorbance
• D. Neutral density filters

Answer: (A)

Stray light is unwanted light that reaches the detector outside the intended spectral region, which can skew measurements. To assess how well an instrument blocks such out‑of‑band light, you want a component that sharply separates wavelengths. Sharp cutoff filters have an abrupt transmission edge, effectively blocking wavelengths just beyond the passband while allowing the desired wavelengths to pass. Using these filters, you can set the instrument to a wavelength and look for any signal when the filter should be blocking; any detected light is stray light. This makes sharp cutoff filters the best choice for testing stray light.