Same chapter3 marksDifficulty: Medium
Find the wavelength of the radiation emitted when an electron in a hydrogen atom falls from the third orbit to the second. Take the Rydberg constant as 1.097 × 107 m−1.
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3 marksDifficulty: Medium
Define mass defect and binding energy, and explain why the binding energy per nucleon curve peaks near iron.
Original Khojo Papers practice question — not from a past board paper.
Answer
The mass defect is the difference between the sum of the masses of the free nucleons and the actual mass of the nucleus; the binding energy is the energy equivalent of that difference. The curve rises for the lightest nuclei because adding nucleons increases the number of short-range attractions, and falls for the heaviest because the long-range electrostatic repulsion of the many protons grows faster; the balance is best near iron.
No citable source has been recorded for this record. Treat it as practice material, not as fact.
Explanation
This is why fusion releases energy below the peak and fission above it.
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