1
JEE Advanced 2015 Paper 2 Offline
Numerical
+4
-0
For a radioactive material, its activity A and rate of change of its activity R are defined as $$A = - {{dN} \over {dt}}$$ and $$R = - {{dA} \over {dt}}$$, where N(t) is the number of nuclei at time t. Two radioactive source P(mean life $$\tau$$) and Q (mean life 2$$\tau$$) have the same activity at t = 0. Their rate of change of activities at t = 2$$\tau$$ are RP and RQ, respectively. If $${{{R_P}} \over {{R_Q}}} = {n \over e}$$, then the value of n is
2
JEE Advanced 2015 Paper 1 Offline
Numerical
+4
-0
Consider a hydrogen atom with its electron in the nth orbital. An electromagnetic radiation of wavelength 90 nm is used to ionize the atom. If the kinetic energy of the ejected electron is 10.4 eV, then the value of n is (hc = 1242 eV nm)
3
JEE Advanced 2015 Paper 1 Offline
Numerical
+4
-0

A nuclear power plant supplying electrical power to a village uses a radioactive material of half life T years as the fuel.

The amount of fuel at the beginning is such that the total power requirement of the village is 12.5 % of the electrical power available from the plant at that time. If the plant is able to meet the total power needs of the village for a maximum period of nT years, then the value of n is

4
JEE Advanced 2013 Paper 1 Offline
Numerical
+3
-0

A freshly prepared sample of a radioisotope of half-life 1386 s has activity 103 disintegrations per second. Given that ln2 = 0.693, the fraction of the initial number of nuclei (expressed in nearest integer percentage) that will decay in the first 80 s after preparation of the sample is __________.