WAEC Past Questions and Answers - Page 3239

16,191.

Which of the following phenomena supports the theory that waves have a particle nature?

A.

electron diffraction

B.

photoelectric effect

C.

diffraction of light

D.

x-ray interference

Correct answer is B

The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material. Electrons emitted in this manner are called photoelectrons.

16,192.

Which of the following statements about the use of radioisotopes is not correct? They are used to

A.

induce mutations in plants and animals to obtain new and improved varieties

B.

trace the paths of metabolic processes in plants and animals

C.

estimate the age of rocks

D.

locate broken bones

Correct answer is A

No explanation has been provided for this answer.

16,193.

Which of the following particles are termed nucleons in a neutral atom?

A.

protons and neutrons

B.

neutrons and electrons

C.

protons and electrons

D.

protons, electrons and neutrons

Correct answer is A

No explanation has been provided for this answer.

16,194.

The minimum energy required to cause photoelectric emission when the surface of a metal is irradiated with electromagnetic radiation of suitable frequency is called

A.

critical energy

B.

ionization energy

C.

work function

D.

planck's constant

Correct answer is C

No explanation has been provided for this answer.

16,195.

The work function of a metal is 2.56 x 10-19J. Calculate the frequency of a photon whose energy is required to eject from the metal an electron with kinetic energy of 3.0ev. [1 eV = 1.6 x 10-19J, h = 6.6 x 10-34Js]

A.

5.56 x 1019Hz

B.

1.66 x 1019Hz

C.

1.12 x 1015Hz

D.

8.42 x 1014Hz

Correct answer is C

F = \(\frac{K.E + Wo}{h}\)

= \(\frac{3.0 \times 1.6 \times 10^{-19} + 2.56 \times 106{-19}}{6.6 \times 106{-34}}\)

- 1.12 x 10-15HZ