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Physics Past Questions and Answers

Waec Physics Questions

Question 691:

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

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A V
B IV
C III
D II

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Question 692:

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?

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

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Question 693:

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)

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

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Question 694:

The half-life of a radioactive substance is

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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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Question 695:

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

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

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