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Nuclei

Multiple Choice Questions

261.

A proton is about 1840 times heavier than an electron. When it is accelerated by a potential difference of 1 kV, its kinetic energy will be

1840 keV
1/1840 keV
1 keV
920 keV

262.
A radioactive substance decays to 1/16^thof its initial activity in 40 days. The half-life of the radioactive substance expressed in days is

2.5

5

10

20

We know that the activity of radioactive substance

A = A_o e^-λt

⇒ $\frac{A}{A_{o}} = e^{- λt} = e^{- \frac{0.693}{T^{\frac{1}{2}}} t}$

$[∵ T_{\frac{1}{2}} = \frac{0.693}{λ}]$

⇒ $\frac{1}{16} = e^{- \frac{0.693}{T^{\frac{1}{2}}} t}$

⇒ $\frac{0.693 \times 40}{T_{\frac{1}{2}}}$ = ln 16

⇒ T_1/2 = $\frac{0.693 \times 40}{\ln 16}$

⇒ = 9.97

⇒ T_1/2 ≈ 10 days

263.

A neutron makes a head-on elastic collision with a stationary deuteron. The fractional energy loss of the neutron in the collision is

16/81
8/9
8/27
2/3

264.

Nuclear fusion is possible

only between light nuclei
only between heavy nuclei
between both light and heavy nuclei
only between nuclei which are stable against β-decay

265.

Radioactive nuclei that are injected into a patient collect at certain sites within its body, undergoing radioactive decay and emitting electromagnetic radiation. These radiations can then be recorded by a detector. This procedure provides an important diagnostic tool called

gamma camera
CAT scan
radiotracer technique
gamma ray spectrosccopy

266.

In a material medium, when a positron meets an electron both the particles annihilate leading to the emission of two gamma ray photons. This process forms the basis of an important diagnostic procedure called

MRI
PET
CAT
SPECT

267.

Assertion: Radioactive nuclei emit β^- particles.

Reason: Electrons exist inside the nucleus.

if both assertion and reason are true and the reason is the correct explanation of the assertion
if both assertion and reason are true and the reason is not the correct explanation of the assertion
if assertion is true but reason is false
If both assertion and reason are false statements

268.

Assertion: Neutrons penetrate matter more readily as compared to protons.

Reason: Neutrons are slightly more massive than protons.

if both assertion and reason are true and the reason is the correct explanation of the assertion
if both assertion and reason are true and the reason is not the correct explanation of assertion
if assertion is true but reason is false
if both assertion and reason are false statements

269.

Assertion: Quasar emits radiowaves more than radio galaxy.

Reason: Quasar has very small size

If both the assertion and reason are true and reason is a correct explanation of the assertion.
If both assertion and reason are true but assertion is not a correct explanation of the assertion.
If the assertion is true but the reason is false.
If both assertion and reason are false.