(a) Define nucleon number
(b) A radioactive isotope of Americium (Am —241) decays into a nucleus of Neptunium (Np — 237) and an alpha (\(\alpha\)) particle as shown in the nuclear equation below. \(^{241}_{95}Am\) \(\to\) \(^{237}_{c} + ^b_a \alpha\)
(i) State the number of neutrons in the nucleus of Americium — 241.
(ii) Determine the values of a,b and c.
(c)(i) Why are y-rays not deflected by electromagnetic field?
(ii) State two properties of gamma rays that make them suitable for sterilizing medical equipment.
(d) A sample of radioactive substance was found to be left with h of its initial count rate after 110 years. Calculate its decay constant.
Verified Correct Answer: .
Physical Principles & Numerical Solution
(a) Nucleon number is the total number of protons and neutrons in the nucleus of an atom.
(b)(i) Number of neutrons in the nucleus of Americium = 241 - 90 =146.
(ii) a = 2
b = 4
c = 95 - 2
= 93.
(c)(i) Y-ray are electrically neutral or carry no charge.
(ii) properties of gamma rays that makes them suitable for medical sterilization of equipment are:
(1) Possession of strong penetrating power.
(2) Posession of low ionizing power.
(d) \(\frac{N}{N_o} = (\frac{1}{2})^a = \frac{1}{32} = (\frac{1}{2})^a\) = (\(\frac{1}{2})^5\)
But T\(_\frac{1}{2}\) = \(\frac{t}{n} = \frac{110}{5}\) = 22 years
Hence \(\lambda\) = \(\frac{0.693}{T_{\frac{1}{2}}} = \frac{0,693}{22}\)
Decay constant \(\lambda\) 3.2 x 10\(^{-2}\) per year
Source: Myschool Past Questions Archive (Record #52993)