Waec Physics 1991 Past Questions and Answers

Question 56:

• WAEC 1991

When a metal surface is irradiated, photoelectrons may be ejected from the metal. The kinetic energy of the ejected electrons depends on the

A. Sorce of the radiation
B. Intensity of the radiation
C. Detection device for the electrons
D. Amplitude of the radiation
E. Frequency of the radiation

Question 57:

• WAEC 1991

An electron charge 1.6 x 10^-19C is accelerated in vacuum from rest at zero volt towards a plate at 40k V. Calculate the kinetic energy of the electron

A. 4.0 x 10^-26J
B. 4.0 x 10^-21J
C. 6.4 x 10^-20J
D. 3.2 x 10^-15J
E. 2.5 x 10^-20J

Question 58:

• WAEC 1991

The half-life of a radioactive substance is 2 seconds. Calculate the decay constant

A. 0.035s^-1
B. 0.151s^-1
C. 0.347s^-1
D. 0.576s^-1
E. 1.386s^-1

Question 59:

• WAEC 1991

The work function of a metal is 4.65ev and the metal is illuminated with a radiation of 6.86ev. What is the kinetic energy of the electrons ejected from the surface of the metal?

A. 1.48ev
B. 2.21ev
C. 4.42ev
D. 5.75ev
E. 11.51ev

Question 60:

• WAEC 1991

Which of the following has the highest surface tension?

A. Cold water
B. Soapy water
C. Warm water
D. Oily water
E. Salty water