Physics 1988 Waec Past Questions and Answers

Question 56 :

• WAEC 1988

(a) Draw a labelled diagram of a vacuum flask. Explain how its construction minimizes heat exchange with the surroundings.
(b) State Boyle's law. A thread of mercury of length 15cm is used to trap some air in a capillary tube with uniform cross- sectional area and closed at one end with the tube vertical and the open end uppermost, the length of the trapped air column is 20cm. Calculate the length of the air column when the tube is held:
(i) Horizontally ; (ii) vertically with the open end underneath. [Atmospheric pressure = 76cm Hg]
(c) Explain why it is not advisable to sterilize a clinical thermometer in boiling water at normal atmospheric pressure.

Question 57 :

• WAEC 1988

(a) Explain with the aid of a diagram how a converging lens could be used to : (i) ignite a piece of carbon paper ; (ii) produce an enlarged picture on a screen ; (iii) correct an eye defect.
(b) What is a mechanical wave? Describe with the aid of a diagram, an experiment to show that sound needs a material medium for transmission.
State 3 characteristics of sound and mention the factor on which each depends.