JAMB Physics Past Questions & Answers - Page 365

1,821.

The phenomenon that shows that increase in pressure lowers the melting point can be observed in

A.

sublimation

B.

condensation

C.

coagulation

D.

regelation

Correct answer is D

Regelation means refreezing a phenomenon whereby melted ice free from increased pressure refreezed when they are released from the pressure.

1,822.

A cannon is fired from town X, after how long is the sound heard at a town Y 4.95 km away?

[velocity of sound in the air = 330 ms-1]

A.

30 s

B.

10 s

C.

12 s

D.

15 s

Correct answer is D

V = X/t
330 = ( 4.95 x 10^3)/t
t = (4.95 x 10^3/330 = 
= 15 secs

1,823.

The ground is always cold at night because the

A.

atmosphere absorbs the sun's energy at night

B.

earth radiates heat to the atmosphere at night

C.

sun no longer shine at night

D.

atmosphere reflects the sun's energy at night

Correct answer is B

The earth radiate heat to the atmosphere at night thereby lowering the temperature of the ground

1,824.

A perfect emitter or absorber of radiant energy is a

A.

conductor

B.

black body

C.

white body

D.

red body

Correct answer is B

Dull, black surface are good emitters or absorbers of energy

1,825.

Which of the following electromagnetic waves has the highest frequency?

A.

utra - violet rays

B.

radio waves

C.

x - rays

D.

infrared - rays

Correct answer is C

r - rays has the highest frequency followed by X - rays, ultraviolet ray, visible light intra - red and the least is radio weaves