Define Radioactivity

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Radioactivity is the act of emitting radiation spontaneously. Radioactivity occurs through an atomic nucleus that is unstable. It "wants" to give up some energy to shift to a more stable configuration.

In Physics. Radioactivity is a nuclear phenomenon of spontaneous emission of α (Alpha) or β (Beta) or γ (Gamma) radiations from the nucleus of atoms during their decay. Uranium and Plutonium exhibit radioactivity and are examples of a radioactive substance.

Radioactivity

Radioactivity

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CBSE CLASS XII Related Questions

  • 1.
    Photoemission of electrons occurs from a metal (\( \phi_0 = 1.96 \, \text{eV} \)) when light of frequency \( 6.4 \times 10^{14} \, \text{Hz} \) is incident on it. Calculate: Energy of a photon in the incident light, The maximum kinetic energy of the emitted electrons, and The stopping potential.


      • 2.
        Draw the number of scattered particles versus the scattering angle graph for scattering of alpha particles by a thin foil. Write two important conclusions that can be drawn from this plot.


          • 3.
            Two small identical metallic balls having charges \( q \) and \( -2q \) are kept far at a separation \( r \). They are brought in contact and then separated at distance \( \frac{r}{2} \). Compared to the initial force \( F \), they will now:

              • attract with a force \( \frac{F}{2} \)
              • repel with a force \( \frac{F}{2} \)
              • repel with a force \( F \)
              • attract with a force \( F \)

            • 4.
              A square loop of side 0.50 m is placed in a uniform magnetic field of 0.4 T perpendicular to the plane of the loop. The loop is rotated through an angle of 60° in 0.2 s. The value of emf induced in the loop will be:

                • 5 V
                • 3.5 V
                • 2.5 V
                • Zero V

              • 5.
                Four independent waves are expressed as \[ (i)\; y_1=A_1\sin\omega t, \] \[ (ii)\; y_2=A_2\sin 2\omega t, \] \[ (iii)\; y_3=A_3\cos\omega t, \] \[ (iv)\; y_4=A_4\sin\left(\omega t+\frac{\pi}{3}\right) \] The interference between two of these waves is possible in

                  • (i) and (iii) only
                  • (iii) and (iv) only
                  • (i), (iii) and (iv) only
                  • All of them

                • 6.
                  If Bohr’s quantization postulate (angular momentum \( = \frac{nh}{2\pi} \)) is a basic law of nature, it should be equally valid for the case of planetary motion also. Why, then, do we never speak of quantization of orbits of planets around the Sun? Explain.

                    CBSE CLASS XII Previous Year Papers

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