WAEC Physics Past Questions & Answers - Page 245

1,221.

The image of an object is located 6cm behind a convex mirror. If its magnification is 0.6, calculate the focal length of the mirror

A.

3.75cm

B.

6.60cm

C.

10.00cm

D.

-15.00cm

Correct answer is D

V = -6cm

M = 0.6cm

Recall m = \(\frac{V}{U}\)

U = \(\frac{V}{M}\)

U = \(\frac{6}{0.6}\)

 U = 10

  \(\frac{1}{U}\) + \(\frac{1}{V}\) = \(\frac{1}{F}\)

 \(\frac{1}{10}\) + \(\frac{1}{-6}\) = \(\frac{1}{F}\)

\(\frac{-4}{60}\) = \(\frac{1}{F}\)

 F = \(\frac{60}{-4}\)

=  -15cm

1,222.

The air column in a resonance tube is set into resonance by a vibrating tuning fork. The resultant waves in the air column will be

A.

mechanical and transverse

B.

progressive and longitudinal

C.

stationary and transverse

D.

stationary and longitudinal.

Correct answer is D

No explanation has been provided for this answer.

1,225.

Which of the following statements about evaporation is not correct?

A.

The rate of evaporation of a liquid varies with temperature

B.

The molecules of an evaporating liquid have an average speed

C.

Evaporation occurs when faster molecules escape from the surface of a liquid

D.

Evaporation takes place inside a liquid.

Correct answer is D

No explanation has been provided for this answer.