Modern Physics-05-SUBJECTIVE UNSOLVED (C.B.S.E.) LEVEL – I

SUBJECTIVE UNSOLVED (C.B.S.E.) LEVEL – I (REVIEW YOUR CONCEPTS) 1. Using the Rydberg formula, calculate the wavelength of the first four spectral lines in the Balmer series of the hydrogen spectrum. 2. Find the energies in units of for the ground state and the first excited state for an electron confined to a line of length m and also find the energies in units of for the ground state and the first excited states of a neutron confined to a line of length m. 3. A beam of 35.0 keV electrons strikes a molybdenum (42 M096 target. What is the cut-off wavelength of the X-rays generated? 4. Using Bohr’s formula for energy quantization, determine (i) the longest wavelength in the Lyman series of hydrogen atom spectrum. (ii) the excitation energy of the level of atom. (iii) the ionization potential of the ground state of atom. 5. The wavelength of the line emitted by hydrogen-like element is 0.32Å. Determine the wavelength of the line emitted by the same element. 6. The total energy of an electron in the first excited state of the hydrogen atom is about ¬ 3.4 eV. (a) What is the kinetic energy of the electron in this state? (b) What is the potential energy of the electron in this state? (c) Which of the answer above would change if the choice of the zero of potential energy is changed? (d) Calculate the wavelength of light emitted if an electron makes a transition to the ground state. [Ground state energy eV] 7. (a) An X-ray tube produces a continuous spectrum of radiation with its short wavelength end at 0.45 Å. What is maximum energy of a photon in the radiation? (b) From your answer to (a), guess what order of accelerating voltage (for electrons) is required in such a tube? 8. The half-life of against alpha decay is years. How many disintegrations per second occur in 1g of ? 9. The nucleus is unstable against decay with a half-life of about years. Write down the equation of the decay and estimate the kinetic energy of the emitted -particle from the following data: . Assume 1u = 931 MeV/c2 10. The neutron separation energy is defined to be the energy required to remove a neutron from a nucleus. Obtain the neutron separation energies of the nuclei and from the following data: , u, , . Assume 1u = 931 MeV/c2

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