Which instrument can be assumed to have the narrower bandpass?

The correct choice is based on the principle that a narrower bandpass in a spectrophotometer allows for greater accuracy and sensitivity when measuring the absorbance of a specific wavelength of light. In this context, the premise is that instruments with superior performance at specific wavelengths often indicate the instrument's capability to discriminate between closely spaced wavelengths.

In this case, the instrument that provides the highest absorbance for a solution of 0.1 mmol/L NADH at 340 nm suggests that it is effectively measuring the absorption at a very specific wavelength where this compound shows strong absorbance. This could indicate that the bandpass is narrower, as it is efficiently capturing light at that exact wavelength rather than allowing broader ranges of wavelengths to interfere. A high absorbance reading suggests that the light being absorbed is predominantly at the targeted wavelength, reinforcing the idea that this instrument is selective for that particular range.

Other choices relate to different measurements or conditions but do not specifically highlight the precision at a defined wavelength in the same way. For instance, the option discussing the highest %T reading indicates transmittance, which can be influenced by multiple factors including sample path length, concentration of absorbing species, and overall light intensity, but it does not inherently indicate the sharpness of the wavelength resolution