# Spectroscopy MCQ Questions & Answers

Spectroscopy MCQs : This section focuses on the "Spectroscopy". These Multiple Choice Questions (MCQs) should be practiced to improve the Spectroscopy skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.

Question 1

Why must the voltage supplied to a tungsten lamp be very stable?

A. Because if it wasn't, the lamp would bum out
B. Because amount of energy the lamp emits is proportional to the fourth power of the operating voltage
C. Because the lamp will only function at a specific voltage
D. All of the above

Question 2

UV-Vis spectroscopy of organic compounds is usually concerned with which electronic transition(s)?

A. σ → σ*
B. n → σ*
C. n → π* and π → π*
D. none of these

Question 3

Beer's Law states that

A. absorbance is proportional to both the path length and concentration of the absorbing species
B. absorbance is proportional to the log of the concentration of the absorbing species
C. absorbance is equal to P0 / P
D. none of the above

Question 4

Which of the following will oscillate the fastest?

A. A large mass on a weak spring
B. A large mass on a stiff spring
C. A small mass on a stiff spring
D. A small mass on a weak spring

Question 5

Why is it generally preferable to use absorbance as a measure of absorption rather than % transmittance?

A. Because %T cannot be measured as accurately as absorbance
B. Because %T is dependant on the power of the incident radiation
C. Because absorbance is proportional to the concentration of the analyte, whereas %T is not
D. none of the above

Question 6

In the past, IR spectra had to be aquired one wavelength at a time, which took a long time. Today quick spectra is due to the

A. the Fourier Transfer Algorithm allows us to scan all frequencies at once
B. light is faster today that it used to be
C. absence of broad spectrum of wavelenth
D. none of the above

Question 7

Why are rotational transitions of little use to a spectroscopist?

A. Because the energy required to induce a rotational transition is so small that it cannot be measured
B. Because rotational transitions are extremely rare
C. Because, in liquids and solids, spectral lines corresponding to rotational transitions are broadened as the result of molecular collisions and other interactions
D. All of the above

Question 8

Which of the following relationships between absorbance and %transmittance is incorrect?

A. A = log10 100 / %T
B. A = 2 - log10 %T
C. A = log10 1 / T
D. All are correct

Question 9

Vibrational spectroscopy is

A. a large mass on a weak spring
B. a flashlight through a prism and shake it
C. a class of spectroscopic techniques which analyzes molecular motions
D. an Infrared spectroscopy

Question 10

A simple harmonic oscillator may absorb energy

A. at anytime.
B. when the frequencies match exactly
C. when the amplitudes are the same.
D. at no time.

Question 11

Which of the following is not an IR vibrational mode?

A. Stretching
B. Scissoring
C. Rocking
D. Rolling

Question 12

Where does a carbonyl (C=0) stretch appear in an IR spectrum?

A. 1740-1720
B. 1870-1650
C. 3640-3250
D. 160-110

Question 13

Which of the following components of a monochromator is the dispersing element?

A. The collimating lens
B. The entrance slit
C. The diffraction grating
D. None of these

Question 14

Molar absorbtivity is the measure of the

A. amount of light absorbed per unit length
B. amount of light absorbed per unit concentration
C. amount of light reflected and absorbed per unit concentration
D. None of the above

Question 15

In the equation, A = ε bc, what quantity is represented by "ε"?

A. Absorbtivity
B. Molar absorbtivity
C. Path length
D. None of these