WAEC Physics Past Questions & Answers - Page 23

111.

Which of the arrangements of radiations below shows decreasing order of wavelengths?

A.

X-rays> radio waves > infrared radiations

B.

Radio waves> infrared radiations > X-rays

C.

Infrared radiations > radio waves > X-rays

D.

X-rays> infrared radiations > radio waves

Correct answer is B

radio waves have a longer wavelength than infrared light, and infrared than x-rays in the electromagnetic spectrum

112.

The components of vectors Q and R are (-3.0, 5.5) and (9.2, 4.4) respectively. Determine the components of Q + R.

A.

(3.7, 7.4)

B.

(6.2, 9.9)

C.

(2.5, -4 .8).

D.

(14.7, 1.4)

Correct answer is B

No explanation has been provided for this answer.

113.

Which of the following curved surfaces will produce a real image? I. Concave mirror II. Convex mirror III. Diverging lens IV. Converging lens

A.

I and III only

B.

I, II and IV only

C.

II, III and V only

D.

II and IV only

Correct answer is D

Convex (converging) lenses can form either real or virtual images, whereas concave (diverging) lenses can form only virtual images

114.

Determine the speed of the wave.

A.

64 cm/s

B.

32 cm/s

C.

24 cm/s

D.

72 cm/s

Correct answer is D

Speed = Wavelength x Frequency

or

 V = fλ, where frequency = 1/period, f = 1/T.

The period was given as 0.125sec and wavelength = 9cm

: f = 1/T = 1/0125 = 8.

 V = fλ = 8 × 9 = 72m/s