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Mere Teacher · Previous Year Questions NEET Physics · Atoms · Set 1 (Q1-30)
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1. $In a hypothetical fission reaction_{92} U^{235} +_{0} n^{1} \to_{56} Y^{141} +_{36} Z^{92} + 3 R The identity of emitted particles (R) is:$ (1) $Electron$ (2) $Neutron$ (3) $γ -radiations$ (4) $Proton$ 2. $When an electron jumps from the orbit n = 2 to n = 4, then wavelength of the radiations absorbed will be (R is Rydberg's constant)$ (1) $16/3 R$ (2) $16/5 R$ (3) $5 R /16$ (4) $3 R /16$ 3. $In a hydrogen atom the electron makes a transition from (n + 1)^{th} level on the n^{th} level. If n >> 1, the frequency of radiation emitted is proportional to:$ (1) $\frac{1}{n}$ (2) $\frac{1}{n ^{2}}$ (3) $\frac{1}{n ^{3}}$ (4) $\frac{1}{n ^{4}}$ 4. $When an electron in Hydrogen atom revolves in stationary orbit, it$ (1) $does not radiate light though its velocity changes$ (2) $does not radiate light and velocity remains unchanged$ (3) $radiates light but its velocity is unchanged$ (4) $radiates light with the change of energy$ 5. $The transition of an electron in hydrogen atom that emits a photon whose wavelength lies in the ultraviolet region of the electromagnetic spectrum is$ (1) $5 \to 4$ (2) $4 \to 3$ (3) $3 \to 2$ (4) $2 \to 1$ 6. $Given below are two statements: Statement (I): The dimensions of Planck's constant and angular momentum are same. Statement (II): In Bohr's model electron revolve around the nucleus only in those orbits for which angular momentum is integral multiple of Planck's constant. In the light of the above statements, choose the most appropriate answer from the options given below:$ (1) $Both Statement I and Statement II are correct$ (2) $Statement I is correct but Statement II is incorrect$ (3) $Both Statement I and Statement II are incorrect$ (4) $Statement I is incorrect but Statement II is correct$ 7. $Speed of an electron in Bohr's 7^{t h} orbit for Hydrogen atom is 3.6 x 1 0^{6} m/s. The corresponding speed of the electron in 3^{r d} orbit, in m/s is:$ (1) $1.8 x 1 0^{6}$ (2) $7.5 x 1 0^{6}$ (3) $3.6 x 1 0^{6}$ (4) $8.4 x 1 0^{6}$ 8. $When the wavelength of the radiation falling on a metal is changed from 500nm to 200 nm, the maximum kinetic energy of the photoelectrons becomes three times larger. The work function of the metal is close to$ (1) $0.52 eV$ (2) $1.02 eV$ (3) $0.61 eV$ (4) $0.81 eV$ 9. $Considering the Bohr's model of hydrogen atom, the ratio of velocities of electrons orbiting in the 4^{th} orbit to that in the 9^{th} orbit is$ (1) $9 : 4$ (2) $3 : 2$ (3) $2 : 3$ (4) $4 : 9$ 10. $Substance A has atomic mass number 16 and half life of 1 day. Another substance B has atomic mass number 32 and half life of \frac{1}{2} day. If both A and B simultaneously start undergo radio activity at the same time with initial mass 320 g each, how many total atoms of A and B combined would be left after 2 days.$ (1) $3.38 x 1 0^{24}$ (2) $6.76 x 1 0^{24}$ (3) $6.76 x 1 0^{23}$ (4) $1.69 x 1 0^{24}$ 11. $The radius of electron's second stationary orbit in Bohr's atom is R. The radius of 3rd orbit will be$ (1) $\frac{R}{3}$ (2) $2.25R$ (3) $3R$ (4) $9R$ 12. $The ratio of the radii of the nuclei_{13} Al^{27} and_{52} T e^{125} approximately$ (1) $6 : 10$ (2) $13 : 52$ (3) $40 : 177$ (4) $14 : 73$ 13. $Electrons used in a electron microscope are accelerated by a voltage of 25 kV. If the voltage is increased to 100kV then the de-Broglie wavelength associated with the electrons would:$ (1) $increases by 2 times$ (2) $decrease by 2 times$ (3) $decrease by 4 times$ (4) $increases by 4 times$ 14. $The valence electron in alkali metal is a$ (1) $f ‐electron$ (2) $p ‐electron$ (3) $s ‐electron$ (4) $d ‐electron$ 15. $Two electrons are moving in orbits of two hydrogen like atoms with speeds 3 \times 10^{5} m / s and 2.5 \times 10^{5} m / s respectively. If the radii of these orbits are nearly same then the possible order of energy states are____respectively.$ (1) $8 and 10$ (2) $9 and 8$ (3) $10 and 12$ (4) $6 and 5$ 16. $_{92}^{238} A \to_{90}^{234} B +_{2}^{4} D + Q In the given nuclear reaction, the approximate amount of energy released will be: [Given, mass of_{92}^{238} A = 238.05079 \times 931.5 MeV c^{- 2}, mass of_{90}^{234} B = 234.04363 \times 931. 5 MeVc^{- 2}, mass of_{2}^{4} D = 4.00260 \times 931.5 MeV c^{- 2}]$ (1) $3.82 MeV$ (2) $5.9 MeV$ (3) $2.12 MeV$ (4) $4.25 M V$ 17. $Hydrogen atom is excited from ground state to another state with principal quantum number equal to 4. Then the number of spectral lines in the emission spectra will be :$ (1) $2$ (2) $3$ (3) $5$ (4) $6$ 18. $If radius of the_{12}^{27} Al nucles is taken to be R_{Al} then the radius of_{53}^{125} Te nucleus is nearly :$ (1) $\frac{5}{3} R_{AI}$ (2) $\frac{3}{5} R_{AI}$ (3) $(\frac{13}{53})^{1/3} R_{AI}$ (4) $(\frac{53}{13})^{1/3} R_{Al}$ 19. $Two radiations of photons energies 1 eV and 2.5 eV, successively illuminate a photosensitive metallic surface of work function 0.5 eV. The ratio of the maximum speeds of the emitted electrons is:$ (1) $1 : 4$ (2) $1 : 2$ (3) $1 : 1$ (4) $1 : 5$ 20. $The shortest wavelength in Balmer series of hydrogen atom spectrum is approximately equal to (use R_{H} = 1.097 \times 10^{7} m^{- 1})$ (1) $3646Å$ (2) $912Å$ (3) $364.6Å$ (4) $91.2Å$ 21. $The threshold frequency for a photosensitive metal is 3.3 \times 10^{14} Hz . If light of frequency 8.2 \times 10^{14} Hz is incident on this metal, the cut-off voltage for the photoelectric emission is nearly$ (1) $2 V$ (2) $3 V$ (3) $5 V$ (4) $1 V$ 22. $The total energy of an electron in the first excited state of hydrogen atom is about - 3.4 eV . Its kinetic energy in this state is$ (1) $3. 4 eV$ (2) $6. 8 eV$ (3) $- 3.4 eV$ (4) $- 6.8 eV$ 23. $In the spectrum of hydrogen, the ratio of the longest wavelength in the Lyman series to the longest wavelength in the Balmer series is$ (1) $\frac{4}{9}$ (2) $\frac{9}{4}$ (3) $\frac{27}{5}$ (4) $\frac{5}{27}$ 24. $Electrons in a certain energy level n = n_{1}, can emit 3 spectral lines. When they are in another energy level, n = n_{2} . They can emit 6 spectral lines. The orbital speed of the electrons in the two orbits are in the ratio$ (1) $4 : 3$ (2) $3 : 4$ (3) $2 : 1$ (4) $1 : 2 .$ 25. $Energy of an electron in the second orbit of hydrogen atom is E_{2} . The energy of electron in the third orbit of He^{+} will be$ (1) $\frac{9}{16} E_{2}$ (2) $\frac{16}{9} E_{2}$ (3) $\frac{3}{16} E_{2}$ (4) $\frac{16}{3} E_{2}$ 26. $The nucleus_{6} C^{12} absorbs an energetic neutron and emits a beta particle (β). The resulting nucleus is$ (1) $_{7} N^{14}$ (2) $_{7} N^{13}$ (3) $_{5} B^{13}$ (4) $_{6} C^{13}$ 27. $The angular momentum of an electron in a hydrogen atom is proportional to: (Where r is the radius of orbit of electron)$ (1) $r$ (2) $r$ (3) $\frac{1}{r}$ (4) $\frac{1}{r}$ 28. $Radiation, with wavelength 6561Å falls on a metal surface to produce photoelectrons. The electrons are made to enter a uniform magnetic field of 3 x 10^{- 4} T . If the radius of the largest circular path followed by the electrons is 10 mm, the work function of the metal is close to:$ (1) $1.8 eV$ (2) $0.8 eV$ (3) $1.1 eV$ (4) $1.4 eV$ 29. $The energy of the ground electronic state of hydrogen atom is‐ 13.6 eV ne energy of the first excited state will be$ (1) $- 27.2 eV$ (2) $- 52.4 eV$ (3) $- 3.4 eV$ (4) $- 6.8 eV$ 30. $Mass numbers of two nuclei are in the ratio of 4 : 3. Their nuclear densities will be in the ratio of$ (1) $4 : 3$ (2) $(\frac{3}{4})^{\frac{1}{3}}$ (3) $1 : 1$ (4) $(\frac{4}{3})^{\frac{1}{3}}$