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1999 - WAEC Physics Past Questions and Answers - page 5

41

The diagram above illustrates the energy transitions of five electrons of an atom. Which of the transitions will produce the emission of longest wavelength?

A
I
B
II
C
III
D
IV
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42

Which of the transitions will produce the emission of highest frequency?

A
V
B
IV
C
III
D
II
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43

I. All elements emit and absorb characteristic spectra. II. Spectral analysis is an important method of identifying environmental pollutants. III. The chemical composition of stars could be determined using spectral analysis. Which of the statements above are correct?

A
I, II and III
B
II and III only
C
I and III only
D
I and II only
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44

A metal has work function of 4.375 eV Calculate its threshold frequency. (h = 6.6 x 10-34Js; 1eV = 1.6 x 10-19J)

A
2.01 X 1015Hz
B
1.06x1015Hz
C
6.30 x 1014Hz
D
1.60 x 1014Hz
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45

The half-life of a radioactive substance is

A
its average life time
B
one-half the value of its decay constant.
C
the length of time needed by the substance to decay completely
D
the length of time during which the activity of the substance reduces by 50%.
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46

The half-life of a radioactive element is 5 Calculate its decay constant

A
0.113s-1
B
0.436 s-1
C
0.139 s-1
D
0.193 s-1.
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47

A sheet of paper is placed in the path of the following radiations: I. Alpha particles II. Beta particles III. Gamma rays. Which of the radiations will pass through the sheet of paper?

A
I only
B
II only
C
I and II only
D
II and III only
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48

Which of the following are the essential parts of an atomic bomb?

A
Uranium and neutrons
B
Radium and polonium
C
Nitrogen and neutrons
D
ranium and α - particles.
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49

Which of the following is not a safety precaution in a nuclear station?

A
Radioactive materials are stored in glass casings
B
Radioactive materials are handled with remote-controlled tongs
C
Technicians in nuclear stations wear radio-sensitive badges which are checked regularly.
D
Radioactive materials are kept in thick-walled lead containers
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