WAEC Past Questions and Answers - Page 3509

17,542.

Which of the following optical instruments does not depend on the use of plane mirrors?

A.

kaleidoscope

B.

simple microscope

C.

sextant

D.

simple periscope

Correct answer is B

No explanation has been provided for this answer.

17,543.

Radio waves travel in air at 3.0 x 108ms-1. If the waves enter water of refractive index \(\frac{4}{3}\), calculate the speed of radio waves in water

A.

4.33 x 108ms-1

B.

4.00 x 108ms-1

C.

2.25 x 108ms-1

D.

1.33 x 108ms-1

Correct answer is C

\(_an_w = \frac{4}{3} = \frac{\text{speed of light in air}}{\text{speed of light in water}}\)

\(\frac{4}{3} = \frac{3 \times 10^8}{x}\)

x = \(\frac{9 \times 10^4}{4}\)

= 2.25 x 108m/s

17,544.

The distance between two points in phase on a progressive wave is 5cm. If the sped of the wave is 0.2ms-1, calculate its period

A.

4.00s

B.

2.50s

C.

0.25s

D.

0.04s

Correct answer is C

F = \(\frac{v}{\lambda} = \frac{0.2}{5 \times 10^{-2}} = 4Hz\)

T = \(\frac{1}{f} = \frac{1}{4} = 0.25s\)

17,545.

Which of the following statements about a progressive mechanical wave is correct?

A.

it can be a plane polarised

B.

its energy is localised at specific points of its profile

C.

it does not require a material medium for its propagation

D.

its frequency remains constant as it travels between different media

Correct answer is D

No explanation has been provided for this answer.