Question:
The half life of a radioactive substance is 20 minutes. In how much time the activity of substance drops to \((\frac{1}{16})^{th}\) of its initial value?
The half life of a radioactive substance is 20 minutes. In how much time the activity of substance drops to \((\frac{1}{16})^{th}\) of its initial value?
Updated On: Jul 1, 2024
- 80 minutes
- 20 minutes
- 40 minutes
- 60 minutes
Hide Solution
Verified By Collegedunia
The Correct Option is A
Solution and Explanation
The correct option is (A): 80 minutes
Left fraction of activity = \(\frac{1}{16}\)
\(\frac{R}{R_0}=(\frac{1}{2})^{\frac{t}{2}}\)
\(\frac{1}{16}=(\frac{1}{2})^{\frac{t}{2}}\)
\((\frac{1}{2})^4=(\frac{1}{2})^{\frac{t}{2}}\)
\(4=\frac{t}{20}\)\(\Rightarrow\)\(t=80\)
Was this answer helpful?
9
2
Top Questions on Atomic Physics
- An electron in the ground state of the hydrogen atom has the orbital radius of \( 5.3 \times 10^{-11} \, \text{m} \) while that for the electron in the third excited state is \( 8.48 \times 10^{-10} \, \text{m} \). The ratio of the de Broglie wavelengths of the electron in the ground state to that in the excited state is:
- JEE Main - 2025
- Physics
- Atomic Physics
- An electron in Bohr model of hydrogen atom makes a transition from energy level \(-1.51 \, \text{eV}\) to \(-3.40 \, \text{eV}\). Calculate the change in the radius of its orbit. The radius of orbit of electron in its ground state is \(0.53 \, \text{\AA}\).
- CBSE CLASS XII - 2025
- Physics
- Atomic Physics
- Assertion (A): The potential energy of an electron revolving in any stationary orbit in a hydrogen atom is positive.
Reason (R): The total energy of a charged particle is always positive.- CBSE CLASS XII - 2025
- Physics
- Atomic Physics
- Given below are two statements:
Statement I: Atoms are electrically neutral as they contain equal number of positive and negative charges.
Statement II: Atoms of each element are stable and emit their characteristic spectrum.
In the light of the above statements, choose the most appropriate answer from the options given below- NEET (UG) - 2024
- Physics
- Atomic Physics
- A particular hydrogen-like ion emits the radiation of frequency $3 \times 10^{15}$ Hz when it makes a transition from $n = 2$ to $n = 1$. The frequency of radiation emitted in the transition from $n = 3$ to $n = 1$ is \[\frac{x}{9} \times 10^{15} \, \text{Hz}, \, \text{when} \, x = _____ .]
- JEE Main - 2024
- Physics
- Atomic Physics
View More Questions
Questions Asked in NEET exam
- Given below are two statements :
Statement I : Bone marrow is the main lymphoid organ where all blood cells including lymphocytes are produced.
Statement II : Both bone marrow and thymus provide micro environments for the development and maturation of T-lymphocytes.
In the light of above statements, choose the most appropriate answer from the options given below :- NEET (UG) - 2024
- Organ And Organ System
- The type of conservation in which the threatened species are taken out from their natural habitat and placed in special setting where they can be protected and given special care is called;
- NEET (UG) - 2024
- Biodiversity
- Given below are two statements:
Statement I: In C3 plants, some O2 binds to RuBisCO, hence CO, fixation is decreased.
Statement II: In C4 plants, mesophyll cells show very little photorespiration while bundle sheath cells do not show photorespiration.
In the light of the above statements, choose the correct answer from the options given below:- NEET (UG) - 2024
- respiration in plants
- Given below are two statements :
Statement I : In the nephron, the descending limb of loop of Henle is impermeable to water and permeable to electrolytes.
Statement II : The proximal convoluted tubule is lined by simple columnar brush border epithelium and increases the surface area for reabsorption.
In the light of the above statements, choose the correct answer from the option given below :- NEET (UG) - 2024
- Nephrons
Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A : The potential (V) at any axial point, at 2 m distance(r) from the centre of the dipole of dipole moment vector\(\vec{P}\) of magnitude, 4 × 10-6 C m, is ± 9 × 103 V.
(Take \(\frac{1}{4\pi\epsilon_0}=9\times10^9\) SI units)
Reason R : \(V=±\frac{2P}{4\pi \epsilon_0r^2}\), where r is the distance of any axial point, situated at 2 m from the centre of the dipole.
In the light of the above statements, choose the correct answer from the options given below :- NEET (UG) - 2024
- Magnetic Field
View More Questions