Q1. Isotopes of the same element differ in the number of
(a) Protons
(b) Neutrons
(c) Electrons
(d) Positrons
(UPSC Prelims 1980)
Answer: (b) Neutrons
Explanation: Isotopes have the same number of protons but differ in the number of neutrons, resulting in different atomic masses but similar chemical properties.
Q2. Mesons are found in
(a) X-rays
(b) Cosmic rays
(c) frays
(d) None of the above
(UPSC Prelims 1985)
Answer: (b) Cosmic rays
Explanation: Mesons are subatomic particles that are commonly found in cosmic rays, which are high-energy particles originating from outer space. When cosmic rays interact with the Earth’s atmosphere, they produce secondary particles, including mesons.
