Nuclei

Nuclei

Easy Questions

Modern Physics

Dual Nature of Radiation and Matter
Atoms
Nuclei
Semiconductor Electronics : Materials, Devices and Simple Circuits
  1. In a radioactive material the activity at time t1 is R1 and at a later time t2, it is R2. If the decay constant of the material is λ, then








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    Let at time t1 & t2, number of particles be N1 & N2. So,

    R1 =
    dN1
    		= -λN1; R2 =
    dN2
    		= -λ N2
    dtdt

    R1
    		=
    λN1
    		=
    N1
    		= e -λ(t2 - t1)
    R2λN2N1e -λ(t2 - t1)

    R1 = R2eλ(t2 - t1) = R2e-λ(t2 - t1)

    Correct Option: D

    Let at time t1 & t2, number of particles be N1 & N2. So,

    R1 =
    dN1
    		= -λN1; R2 =
    dN2
    		= -λ N2
    dtdt

    R1
    		=
    λN1
    		=
    N1
    		= e -λ(t2 - t1)
    R2λN2N1e -λ(t2 - t1)

    R1 = R2eλ(t2 - t1) = R2e-λ(t2 - t1)

  1. Alpha-particles are








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    We know that alpha particles are the nucleus of ionized helium atoms which contain two protons and two neutrons. These are emitted by the nuclei of certain radioactive substances. Streams of alpha particles, called α-rays, produce intense ionisation in gases through which they pass and are easily absorbed by matter.

    Correct Option: D

    We know that alpha particles are the nucleus of ionized helium atoms which contain two protons and two neutrons. These are emitted by the nuclei of certain radioactive substances. Streams of alpha particles, called α-rays, produce intense ionisation in gases through which they pass and are easily absorbed by matter.

  1. A sample has 4 × 1016 radioactive nuclei of half life 10 days. The number of atoms decaying in 30 days is








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    N = 4 × 1016
    1
    		30/10=
    1
    		× 1016
    22

    Atoms decayed
    = 4 × 1016 -
    1
    		× 1016
    2

    = 3.5 × 1016

    Correct Option: D

    N = 4 × 1016
    1
    		30/10=
    1
    		× 1016
    22

    Atoms decayed
    = 4 × 1016 -
    1
    		× 1016
    2

    = 3.5 × 1016

  1. A deuteron strikes 8O16 nucleus with subseq-uent emission of an alpha particle. Identify the nucleus so produced








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    8O16 + 1H2 → 2He4 + 7N14

    Correct Option: D

    8O16 + 1H2 → 2He4 + 7N14

  1. The decay constant (λ) and the half-life (T) of a radioactive isotope are related as








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    t =
    1
    		log
    a
    λa - x

    When t = T,
    x =
    a
    2

    T =
    1
    		log
    a
    		=
    1
    		loge2
    λa -
    a
    		λ
    2

    ⇒ λ =
    1
    		loge2
    T

    Correct Option: A

    t =
    1
    		log
    a
    λa - x

    When t = T,
    x =
    a
    2

    T =
    1
    		log
    a
    		=
    1
    		loge2
    λa -
    a
    		λ
    2

    ⇒ λ =
    1
    		loge2
    T