wave controls

Question 1

Gain

Q: What does gain control in spectrometers?

Answer 1

It amplifies signal intensity, increasing detector response without changing wavelength.
UV–Vis, IR, MS, ICP, AAS, Raman uses gain
Exam trap: Too much gain → noise amplification.

Question 2

Sensitivity

Q: What does sensitivity adjust?

Answer 2

A: The instrument’s ability to detect low-intensity signals at a given wavelength or m/z.

Used in: MS, ICP-MS, AFS, fluorescence Exam link: Affects detection limit, not accuracy.

Question 3

Wavelength Selection

Q: What does wavelength control do?

Answer 3

A: Selects the specific wavelength used for measurement.

Controlled by: Monochromator / grating / interferometer
Used in: UV–Vis, IR, AAS, AFS, Raman
Exam gold: ε depends on wavelength.

Question 4

Wavelength Shift (Calibration Shift)

Q: What is wavelength shift?

Answer 4

A: A misalignment between true and measured wavelength.

Caused by: Lamp ageing, grating misalignment
Effect: Peaks appear at incorrect wavelengths.

Question 5

Resolution

Q: What does resolution control?

Answer 5

A: The ability to separate closely spaced peaks in wavelength or m/z.

Used in: IR, Raman, MS, XRD
Trade-off: Higher resolution → lower signal intensity.

Question 6

Scan Speed

Q: What does scan speed affect?

Answer 6

A: How fast the instrument scans across wavelengths.

Effect:

Fast scan → lower signal-to-noise

Slow scan → better precision

Question 7

Q: What is integration time?

Answer 7

A: The time the detector collects signal at one wavelength. Effect: Longer time → higher signal, more noise risk.

Question 8

Baseline / Zero

Q: What does baseline correction do?

Answer 8

A: Removes background signal so absorbance/emission is measured correctly.

Used in: UV–Vis, IR, fluorescence
Exam phrase: Background subtraction.

Question 9

Background Correction

Q: What does background correction control?

Answer 9

A: Compensates for non-analyte absorption or emission.

Used in: AAS (D₂ lamp), ICP, fluorescence
Exam win: Improves accuracy, not sensitivity.

Question 10

Interference

Q: What is spectral interference?

Answer 10

A: Overlap of signals at the same wavelength or m/z.

Examples:

UV–Vis: overlapping absorbance

MS: isobaric ions

ICP: polyatomic ions

Question 11

Frequency

Q: Where is frequency most relevant?

Answer 11

A: In techniques based on electromagnetic fields or oscillations.

Used in:

NMR → RF frequency

ICP → RF generator frequency

Raman → laser frequency (fixed)

Question 12

Output Mode

Q: What does output mode control?

Answer 12

A: How results are displayed: absorbance, transmittance, intensity, counts.

Examples:

UV–Vis → Absorbance

MS → Ion counts

ICP → Emission intensity

Question 13

Noise Filtering / Smoothing

Q: What does signal smoothing do?

Answer 13

A: Reduces random noise without changing peak position.

Risk: Excessive smoothing can hide real peaks.