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JAMB Physics Past Questions & Answers - Page 239

1,191.

A lens of focal length 12.0cm forms an upright image three times the size of a real object. The distance between the object and the images is

8.0cm

16.0cm

24.0cm

32.0cm

View answer & explanation

Correct answer is D

F = 12cm, V = 3u

F = $\frac{uv}{u + v}$

12 = $\frac{u\times 3u}{u + 3v}$

u = 16cm, and v = 48cm

therefore, distance between u and v

v = 48 - 16 = 32cm

1,192.

Which of the following is true of sounds?

sound travels faster in air at 20^oC than at 30^oC

the frequency of a given sound wave changes when it crosses the boundary seperating two media

the wavelength of a given sound wave in air decreases as the temperature increases

sound waves cannot be reflected

View answer & explanation

Correct answer is C

No explanation has been provided for this answer.

1,193.

When two objects P and Q are supplied with the same quantity of heat, the temperature change in P is observed to be twice that of Q. The ratio of the specific heat capacity of P to Q is

1 : 4

4 : 1

1 : 1

2 : 1

View answer & explanation

Correct answer is C

$\theta$ _p = 2 $\theta$ q

mq = 2mp

C_p X mp X $\theta$ p = C_q x mq x $\theta$ _q

$\frac {C_pm_q\theta q}{C_qm_p \theta q}$ = $\frac {\theta q \times 2mp}{2 \theta qmp}$

$\frac {C_p}{Cq}$ = $\frac {2}{2}$