Nuclei

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

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

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

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

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.

Mass of the proton is 1840 times that of electron. It is accelerated through a potential difference of 1V. Find its kinetic energy.

• 6 eV

• 2 eV

• 10 eV

• 1 eV

A certain radioactive element has a half-life of 20 years. If we have a block with 10 g of the element in it, after how many years will there be just 2.5 g of the element in the block?

• 80 years

• 40 years

• 100 years

• 60 years

The activity of a radioactive sample decreases to
(1/3)^rd of its original value in 3 days. Then, in 9 days its activity will become

• (1/27) of the original value

• (1/9) of the original value

• (1/18) of the original value

• (1/3) of the original value

If r₁ and r₂  are the radii of the atomic nuclei of mass numbers 64 and 125 respectively, then the ratio (r_1/r₂) is

• 64/125

• $\sqrt{\frac{64}{125}}$

• 5/4

• 4/5

A radioactive element forms its own isotope after 3 consecutive disintegrations. The particles emitted are

• 3 β-particles

• 2 β-particles and 1α-particle

• 2 -βparticles and 1 γ-particle

• 2 α-particles and 1 β-particle