WAEC Physics Past Questions & Answers - Page 215

1,071.

In the electrical method of magnetisation, the polarity of the magnet depends on the

A.

amount of current passed

B.

direction of current

C.

magnetic material used

D.

size of the magnetic material

E.

orientation of the magnetic material in space

Correct answer is B

No explanation has been provided for this answer.

1,072.

The gravitational force of the moon is one-sixth that of the earth. If a body weighs 6.0N on the moon. Calculate its weight on the earth

A.

36.0N

B.

12.0N

C.

6.0N

D.

2.0N

E.

1.0N

Correct answer is A

\(\frac{1}{6}F_E = F_{MOON}\)

FE = R = 6Fm

= 6 x 6 = 36N

1,073.

An electromagnetic wave of frequency 5.0 x 1014Hz, is incident on the surface of water of refractive index \(\frac{4}{3}\). Taking the speed of the wave in air as 3.0 x 108ms-1, calculate the wavelength of the wave in water.

A.

2.2 x 10-6m

B.

1.7 x 10-7m

C.

8.0 x 10-7m

D.

6.0 x 10-7m

E.

4.5 x 10-7m

Correct answer is E

\(_an_w = \frac{\lambda_a}{\lambda_w}\)

\(\frac{4}{3} = \frac{\lambda_a}{\lambda}\)

\(\lambda_w = \frac{v}{f}\)

= \(\frac{3.0 \times 10^8}{5.0 \times 10^{14}} = 0.6 \times 10^{-6}\)

\(\lambda_w = \frac{3}{4} \lambda_a = \frac{3}{4} \times 0.6 \times 10^{-6}\)

= 4.5 x 10-7m

1,074.

Which of the following are both mechanical and transverse?

A.

infra-red rays

B.

gamma rays

C.

sound waves

D.

water waves

E.

micro waves

Correct answer is D

No explanation has been provided for this answer.

1,075.

Calculate the wavelength of a note which is one octave lower than a note of 256Hz in a medium in which the speed of sound is 352ms-1

A.

0.69m

B.

1.38m

C.

2.75m

D.

5.50m

E.

9.30m

Correct answer is B

\(\lambda\) = \(\frac{v}{f} = \frac{352}{256}\)

= 1.38