A:-Only (i) and (iii)
B:-Only (iii) and (iv)
C:-Only (ii) and (iii)
D:-Only (ii) and (iv)
Correct Answer:- Option-D

Question38:-Flame temperature greater than 2000 K is an essential requirement of
flame spectroscopy. Which among the following fuels produce highest flame
temperature?

A:-Acetylene + Air
B:-Hydrogen + Air
C:-Acetylene + Nitrous oxide
D:-Propane + Nitrous oxide
Correct Answer:- Option-C

Question39:-Fluorescence spectrum usually consists of only one band with many
closely spaced lines that corresponds to transition from lowest vibrational levels of
=, to different vibrational levels of = . This is because

A:-Internal conversion and vibrational relaxation process are very slow
compared to fluorescence.

B:-Internal conversion and vibrational relaxation process are very fast
compared to fluorescence.

C:-Vibrational relaxation is very slower than fluorescence.

D:-Internal conversion process is slower but vibrational relaxation is faster
compared to fluorescence.

Correct Answer:- Option-B

Question40:-Molecular fluorescence band mostly consists of lines that are lower in
energy than the band of absorbed radiation. This is termed as

A:-Quenched fluorescence
B:-Anti-Stokes shifted fluorescence
C:-Stokes shifted fluorescence
D:-Enhanced fluorescence

Correct Answer:- Option-C

Question41:-In Scanning Electron Microscopy (SEM), the signals are generated from
(i) Back scattered electrons

(11) Absorbed electrons

(111) Transmitted electrons

(iv) Secondary electrons

A:-Only (i)

B:-Only (iv)
C:-Only (ii) and (iii)
D:-Only (i) and (iv)