Practice Questions

Q17.In a photoelectric effect experiment a light of frequency 1 . 5 times the threshold frequency is made to fall on the surface of photosensitive material. Now if the frequency is halved and intensity is doubled, the number of photo electrons emitted will be: (1) Doubled (2) Quadrupled (3) Zero (4) Halved

Q17.When UV light of wavelength 300 nm is incident on the metal surface having work function 2.13eV, electron emission takes place. The stopping potential is: (Given hc = 1240eVnm ) (1) 1.5 V (2) 4.1 V (3) 2 V (4) 4 V

Q17.Average force exerted on a non-reflecting surface at normal incidence is 2.4 × 10−4 N. If 360 W/cm2 is the light energy flux during span of 1 hour 30 minutes, Then the area of the surface is: (1) 0.2 m2 (2) 20 m2 (3) 0.1 m2 (4) 0.02 m2

Q17.A proton, an electron and an alpha particle have the same energies. Their de-Broglie wavelengths will be compared as : (1) λα < λp < λe (2) λe > λα > λp (3) λp > λe > λα (4) λp < λe < λα

Q17.A biconvex lens of refractive index 1. 5 has a focal length of 20 cm in air. Its focal length when immersed in a liquid of refractive index 1. 6 will be: (1) −16 cm (2) −160 cm (3) +160 cm (4) +16 cm

Q17.The de Broglie wavelengths of a proton and an 𝛼 particle are 𝜆 and 2𝜆 respectively. The ratio of the velocities of proton and 𝛼 particle will be : (1) 1 : 8 (2) 1 : 2 (3) 4 : 1 (4) 8 : 1

Q17.Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R. Assertion A: Number of photons increases with increase in frequency of light. Reason R: Maximum kinetic energy of emitted electrons increases with the frequency of incident radiation. In the light of the above statements, choose the most appropriate answer from the options given below: (1) Both A and R are correct and R is the correct (2) Both A and R are correct and R is NOT the explanation of A. correct explanation of A. (3) A is not correct but R is correct. (4) A is correct but R is not correct.

Q17.Which of the following statement is not true about stopping potential (V0) ? (1) It is 1/ e times the maximum kinetic energy of (2) It increases with increase in intensity of the electrons emitted. incident light. (3) It depends on the nature of emitter material. (4) It depends upon frequency of the incident light.

Q18.The radius of third stationary orbit of electron for Bohr's atom is R. The radius of fourth stationary orbit will be: (1) 4 R (2) 16 R 3 9 (3) 3 R (4) 9 R 4 16

Q18.The energy equivalent of 1 g of substance is : (1) 5.6 × 1012MeV (2) 5.6 × 1026MeV (3) 11.2 × 1024MeV (4) 5.6eV

Q18.Which figure shows the correct variation of applied potential difference (V) with photoelectric current (I) at two different intensities of light (I1 < I2) of same wavelengths : (1) (2) (3) (4)

Q18.The longest wavelength associated with Paschen series is : (Given RH = 1.097 × 107SI unit) (1) 3.646 × 10−6 m (2) 1.876 × 10−6 m (3) 2.973 × 10−6 m (4) 1.094 × 10−6 m

Q18.The atomic mass of 6C12 is 12 . 000000 u and that of 6C13 is 13 . 003354 u. The required energy to remove a neutron from 6C13 , if mass of neutron is 1 . 008665 u, will be: (1) 62 . 5MeV (2) 6 . 25MeV (3) 4 . 95MeV (4) 49 . 5MeV

Q18.When a metal surface is illuminated by light of wavelength 𝜆, the stopping potential is 8 V. When the same surface is illuminated by light of wavelength 3𝜆, stopping potential is 2 V. The threshold wavelength for this surface is : (1) 5𝜆 (2) 3𝜆 (3) 9𝜆 (4) 4 . 5𝜆

Q18. Given below are two statements : Statement I : Figure shows the variation of stopping potential with frequency (v) for the two photosensitive materials M1 and M2 . The slope gives value of h , where h is Planck's constant, e is the charge of electron. Statement II : M2 will emit photoelectrons of e greater kinetic energy for the incident radiation having same frequency. 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 incorrect but Statement II is correct (3) Both Statement I and Statement II are incorrect (4) Statement I is correct and Statement II is incorrect

Q18.The ratio of the shortest wavelength of Balmer series to the shortest wavelength of Lyman series for hydrogen atom is : (1) 4 : 1 (2) 1 : 4 (3) 2 : 1 (4) 1 : 2 JEE Main 2024 (06 Apr Shift 1) JEE Main Previous Year Paper

Q18.Monochromatic light of frequency 6 × 1014 Hz is produced by a laser. The power emitted is 2 × 10-3 W . How many photons per second on an average, are emitted by the source? (Given h = 6 . 63 × 10-34 J s) (1) 9 × 1018 (2) 6 × 1015 (3) 5 × 1015 (4) 7 × 1016

Q18.Two sources of light emit with a power of 200 W. The ratio of number of photons of visible light emitted by each source having wavelengths 300 nm and 500 nm respectively, will be : (1) 1 : 5 (2) 1 : 3 (3) 5 : 3 (4) 3 : 5

Q18.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) 1 (4) 1 √r r

Q19.In the given circuit if the power rating of Zener diode is 10 mW, the value of series resistance 𝑅𝑠 to regulate the input unregulated supply is: 3 (1) 𝑘𝛺 (2) 10 𝛺 7 (3) 1 𝑘𝛺 (4) 10 𝑘𝛺 Q20.10 divisions on the main scale of a Vernier calliper coincide with 11 divisions on the Vernier scale. If each division on the main scale is of 5 units, the least count of the instrument is : (1) 1 (2) 10 2 11 (3) 50 (4) 5 11 11

Q19.In the given circuit, the voltage across load resistance ( 𝑅𝐿) is: (1) 8 . 75 V (2) 9 . 00 V (3) 8 . 50 V (4) 14 . 00 V

Q19.The output of the given circuit diagram is JEE Main 2024 (31 Jan Shift 2) JEE Main Previous Year Paper (1) (2) (3) (4)

Q19.The explosive in a Hydrogen bomb is a mixture of 1H2, 1H3 and 3Li6 in some condensed form. The chain reaction is given by 3Li6 + 0n1 →2He4 + 1H3; 1H2 + 1H3 →2He4 + 0n1 During the explosion the energy released is approximately [Given : M(Li) = 6. 01690 amu, M(1H2) = 2. 01471 amu, M(2He4) = 4. 00388 amu and 1 amu = 931. 5 MeV] (1) 28. 12 MeV (2) 12. 64 MeV (3) 16. 48 MeV (4) 22. 22 MeV

Q19.Which of the following nuclear fragments corresponding to nuclear fission between neutron (10n) and uranium isotope (23592 U) is correct : (1) 144 56 Ba + 8936Kr + 410n (2) 14456 Ba + 8936Kr + 310n (3) 140 56 Xe + 9438Sr + 310n (4) 15351 Sb + 9941Nb + 310n

Q19.From the statements given below : (A) The angular momentum of an electron in 𝑛𝑡ℎ orbit is an integral multiple of ℎ. (B) Nuclear forces do not obey inverse square law. JEE Main 2024 (01 Feb Shift 2) JEE Main Previous Year Paper (C) Nuclear forces are spin dependent. (D) Nuclear forces are central and charge independent. (E) Stability of nucleus is inversely proportional to the value of packing fraction. Choose the correct answer from the options given below : (1) (A), (B), (C), (D) only (2) (A), (C), (D), (E) only (3) (A), (B), (C), (E) only (4) (B), (C), (D), (E) only