List of top Physics Questions on Decay Rate

A radioactive element having half-life (30 min) is undergoing beta decay. The fraction of radioactive element remains undecayed after (90 min) will be

\( 75\% \) of \( ^{234}_{90}\text{Th} \) decays in \( t \) years. Its half-life is (in years):

A radioactive element having half-life (30 min) is undergoing beta decay. The fraction of radioactive element remains undecayed after (90 min) will be

A radioactive element with $6\times10^{5}$ atoms initially is left with $0.75\times10^{5}$ undecayed atoms in $48$ years. The half-life is:

A radioactive element having half-life (30 min) is undergoing beta decay. The fraction of radioactive element remains undecayed after (90 min) will be

If N is the initial number of atoms in a radioactive sample, then the number of atoms decayed after the five half life periods is

Radioactive materials A and B have decay constants ' \( 9\lambda \) ' and ' \( \lambda \) ' respectively. Initially they have same number of nuclei. The ratio of number of nuclei of material ' \( A \) ' to that of ' \( B \) ' will be \( \left( \frac{1}{e} \right) \) after time ' \( t \) '. So ' \( t \) ' is equal to

If the radius of earth is reduced to three-fourth of its present value without change in its mass then value of duration of the day of earth will be ______ hours 30 minutes.

Half life of radio-active element is $1600$ years. The fraction of sample remains undecayed after $6400$ years will be

Half-life period of a radioactive substance is \(10\,\text{min}\). Then amount of substance decayed in \(40\,\text{min}\) will be:

Eight grams of Cu$^{66}$ undergoes radioactive decay and after 15 minutes only 1 g remains. The half-life, in minutes, is then}

A radioactive sample contains \(10^{-3}\,kg\) each of two nuclear species A and B with half-life 4 days and 8 days respectively. The ratio of the amounts of A and B after 16 days is

In an ore containing uranium, the ratio of \(^{238}\text{U}\) to \(^{206}\text{Pb}\) is \(3:1\). Calculate the age of the ore, assuming that all the lead present in the ore is the final stable product of \(^{238}\text{U}\). Take the half-life of \(^{238}\text{U}\) to be \(4.5\times10^9\) yr.

The half-life of a radioactive substance is 20 minutes. The time taken between 50% decay and 87.5% decay of the substance will be

The half-life of a radioactive substance is 20 minutes. The time taken between 50% decay and 87.5% decay of the substance will be

The half-life of a radioactive substance is 20 minutes. The time taken between 50% decay and 87.5% decay of the substance will be

Fraction decayed in 6 days is \(7/8\). Find fraction decayed in 10 days.

The moment of inertia of a body about a given axis is \(1.2\ \text{kg·m}^2\). To produce a rotational kinetic energy of \(1500\ \text{J}\) an angular acceleration of \(25\ \text{rad/s}^2\) must be applied for

A wet open umbrella is held vertical and it whirls about the handle at a uniform rate of 21 revolutions in \(44\ \text{s}\). If the rim of the umbrella is a circle of \(1\ \text{m}\) in diameter and the height of the rim above the floor is \(4.9\ \text{m}\), the locus of the drop is a circle of radius

Rn decays into Po by emitting an \( \alpha \)-particle with half-life of 4 days. A sample contains \( 6.4 \times 10^{10} \) atoms of Rn after 12 days, the number of atoms of Rn left in the sample will be:

Decay constant of radium is \( \lambda \). By a suitable process its compound radium bromide is obtained. The decay constant of radium bromide will be:

A freshly prepared radioactive source of half-life 2 h emits radiation of intensity which is 64 times the permissible safe level. Calculate the minimum time after which it would be possible to work safely with this source.