JAMB Physics Past Questions & Answers - Page 248

1,236.

A heavy object is suspended from a string and lowered into water so that it is completely submerged. The object appears lighter because

A.

the density of water is less than that of the object

B.

the pressure is low just below the water surface

C.

it experiences an upthrust

D.

the tension in the string neutralizes part of the weight

Correct answer is C

No explanation has been provided for this answer.

1,237.

Which of the following represents the correct precision if the length of a piece of wire is measured with a meter rule?

A.

35mm

B.

35.0mm

C.

35.00mm

D.

35.01mm

Correct answer is A

No explanation has been provided for this answer.

1,238.

A radioactive sample initially contains N atoms. After three half-lives the number of atoms that have disintegrated is

A.

\(\frac{N}{8}\)

B.

\(\frac{3N}{8}\)

C.

\(\frac{5N}{8}\)

D.

\(\frac{7N}{8}\)

Correct answer is D

N \(\to\) \(\frac{N}{2}\) \(\to\) \(\frac{N}{4}\) \(\to\) \(\frac{N}{8}\)

 Number of atoms left = 1-1/8=\(\frac{7N}{8}\)

1,239.

Isotopes are nuclei which have

A.

the same number of nuetrons and electrons

B.

equal number of electrons and protons

C.

the same atomic number but different number of neutrons

D.

the same number of total particles

Correct answer is C

No explanation has been provided for this answer.

1,240.

Which of the following statements is TRUE of photoelectric effect?

A.

it cannot occur in liquids

B.

the energy of the emitted electrons is independent of the work function of the surface

C.

the energy of the emitted electron depends on the wavelength of the incident light

D.

the greater the intensity of the incuident light, the greater the incident of the emitted electron

Correct answer is C

The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material.

The frequency of the incident light on the substance determines the kinetic energy of the emitted electrons.

The number of electrons emitted and the intensity of light incident are proportional to each other.