Question
Define the activity of a given radioactive substance. Write its S.I. unit.
✓
Answer
The rate of decay of a radioactive substance is called activity of that substance. It is negative of the rate of decay of the radioactive substance. Activity, $\text{R} = \frac{\text{N}' - \text{N}}{\text{t}' - \text{t}}$ $ = - \frac{\Delta\text{N}}{\Delta\text{t}}$ $ \DeclareMathOperator*{\median}{\text{lim}} \median_{\Delta\text{t}\rightarrow0}\bigg(-\frac{\Delta\text{N}}{\Delta\text{t}}\bigg) = -\frac{\text{dN}}{\text{dt}}$ S.I. unit of activity
- becquerel (Bq).
- decay per second.
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
A hollow metal sphere and a solid metal sphere of equal radii are given equal charges. Which of the two will have higher potential?
Define current density. State its unit.
Choose the correct alternative from the clues given at the end of the each statement:
In the ground state of .......... electrons are in stable equilibrium, while in .......... electrons always experience a net force. (Thomson’s model/ Rutherford’s model.)
In the ground state of .......... electrons are in stable equilibrium, while in .......... electrons always experience a net force. (Thomson’s model/ Rutherford’s model.)
Galileo was punished by the Church for teaching that the sun is stationary and the earth moves around it. His opponents held the view that the earth is stationary and the sun moves around it. If the absolute motion has no meaning, are the two, viewpoints not equally correct or equally wrong?
Write the magnifying power of objective lens.
Four $2\ cm \times 2\ cm \times 2\ cm$ cubes of ice are taken out from a refrigerator and are put in $200\ ml$ of a drink at $10^\circ C.$
→- Find the temperature of the drink when thermal equilibrium is attained in it.
- If the ice cubes do not melt completely, find the amount melted. Assume that no heat is lost to the outside of the drink and that the container has negligible heat capacity. Density of ice $= 900\ kg-m^{-3}$, density of the drink $= 1000\ kg-m^{-3}$, specific heat capacity of the drink $= 4200Jkg^{-1}-K^{-1}$, latent heat of fusion of ice $= 3.4 \times 10^5J-kg^{-1}.$
A sample of $\text{HCI}$ gas is placed in an electric field of $2.5 \times 10^4NC^{-1}.$ The dipole moment of each $\text{HCI}$ molecule is $3.4 \times 10^{-30}Cm.$ Find the maximum torque that can act on a molecule.
→Consider the situation described in the previous problem. Show that the force on the sphere due to the light falling on it is the same even if the sphere is not perfectly absorbing.
In the given diagram, is the diode D forward or reverse biased?
What is geometrical optics?