The operation of a nuclear reactor is said to be critical, if the multiplication factor ( K ) has a value
1
1.5
2.1
2.5
The foil bone has a 14C : 12C ratio, which is [ 1/16 ] of that in a living animal bone. If the half-life time of 14C is 5730 years, then the age of the fossil bone is
11460 years
17190 years
22920 years
45840 years
C.
22920 years
After 5730 years, the number of C14 remaining is th original.
To have ( 1/ 16) original value, it takes (1/2)4, 4 half lives.
Therefore, the bone is 4 × 5730 years = 22920 year old.
If alpha, beta and gamma rays carry same momentum, which has the longest wavelength?
Alpha rays
Beta rays
Gamma rays
None, all have same wavelength
Assertion: The binding energy per nucleon, for nuclei with atomic mass number A > 100 decreases with A.
Reason: The nuclear forces are weak for heavier nuclei.
If both assertion and reason are true and reason is the correct explanation of the assertion
If both assertion and reason are true but reason is not the correct explanation of the assertion
If assertion is true, but reason is false
Both assertion and reason are false statements
Assertion: Cobalt-60 is useful in cancer therapy.
Reason: Cobalt-60 is a source of y-radiations capable of killing cancerous cells.
If both assertion and reason are true and reason is the correct explanation of the assertion
If both assertion and reason are true but reason is not the correct explanation of the assertion
If assertion is true, but reason is false
Both assertion and reason are false statements
The magnetic moment ( μ) of a revolving electron around the nucleus varies with principal quantum number n as
μ ∝ n
μ ∝ 1/n
μ ∝ n2
μ ∝ 1/n2
A radioactive material has a half-life of 10 days. What fraction of the material would remain after 30 days?
0.5
0.25
0.125
0.33
According to Hubble's law, the redshift (Z) of a receding galaxy and its distance r from earth are related as
Z ∝ r
Z ∝ 1/r
Z ∝ 1/r2
Z ∝ r3/2