Practice Questions

Q17.An electron (mass m) with an initial velocity →v= v0ˆi(v0 > 0) is moving in an electric field → E = −E0ˆi(E0 > 0) where E0 is constant. If at t = 0 , de-Broglie wavelength is λ0 = mv0h , then its de-Broglie wavelength after time t is given by (1) λ0 (2) λ0(1 + eE0tmv0 ) (3) λ0t (4) λ0eE0t (1+ mv0 )

Q17.An electron with speed v and a photon with speed c have the same de-Broglie wavelength. If the kinetic energy and momentum of electron are Ee and Pe and that of photon are Eph and Pph respectively. Which of the JEE Main 2022 (26 Jun Shift 1) JEE Main Previous Year Paper following is correct? (1) Eph Ee = 2cv (2) EphEe = 2cv (3) pph pe = 2cv (4) pphpe = 2cv

Q17.A parallel beam of light of wavelength 900 nm and intensity 100 Wm−2 is incident on a surface perpendicular to the beam. The number of photons crossing 1 cm2 area perpendicular to the beam in one second is (1) 3 × 1016 (2) 4. 5 × 1016 (3) 4. 5 × 1017 (4) 4. 5 × 1020

Q17.Which is the correct ascending order of wavelengths? (1) λvisible < λX−ray < λgamma−ray < λmicrowave (2) λgamma−ray < λX−ray < λvisible < λmicrowave (3) λX−ray < λgamma−ray < λvisible < λmicrowave (4) λmicrowave < λvisible < λgamma−ray < λX−ray

Q17.Time taken by light to travel in two different materials 𝐴 and 𝐵 of refractive indices 𝜇𝐴 and 𝜇𝐵 of same thickness is 𝑡1 and 𝑡2 respectively. If 𝑡2 - 𝑡1 = 5 × 10-10s and the ratio of 𝜇𝐴 to 𝜇𝐵 is 1: 2. Then the thickness of material, in meter is: (Given 𝑣𝐴 and 𝑣𝐵 are velocities of light in 𝐴 and 𝐵 materials respectively). (1) 5 × 10-10𝑣𝐴 m (2) 5 × 10-10 m (3) 1 . 5 × 1010 m (4) 5 × 10-10𝑣𝐵 m

Q18.The disintegration rate of a certain radioactive sample at any instant is 4250 disintegrations per minute. 10 minutes later, the rate becomes 2250 disintegrations per minute. The approximate decay constant is (Take loge 1. 88 = 0. 63 ) (1) 0. 02 min−1 (2) 2. 7 min−1 (3) 0. 063 min−1 (4) 6. 3 min−1

Q18.A metal exposed to light of wavelength 800 nm and emits photoelectrons with a certain kinetic energy. The maximum kinetic energy of photo-electron doubles when light of wavelength 500 nm is used. The work JEE Main 2022 (25 Jul Shift 1) JEE Main Previous Year Paper function of the metal is (Take ℎ𝑐= 1230 eV - nm). (1) 1 . 537eV (2) 2 . 46eV (3) 0 . 615eV (4) 1 . 23eV

Q18.The electric field at a point associated with a light wave is given by E = 200[sin(6 × 1015)t + sin(9 × 1015)t] Vm−1 Given: h = 4. 14 × 10−15 eVs If this light falls on a metal surface having a work function of 2. 50 eV , the maximum kinetic energy of the photoelectrons will be (1) 1. 90 eV (2) 3. 27 eV (3) 3. 60 eV (4) 3. 42 eV

Q18.An electric bulb is rated as 200 W. What will be the peak magnetic field at 4 m distance produced by the radiations coming from this bulb? Consider this bulb as a point source with 3. 5% efficiency. (1) 1. 19 × 10−8T (2) 1. 71 × 10−8T (3) 0. 84 × 10−8T (4) 3. 36 × 10−8T

Q18.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) 3 13 4 (3) 1: 1 (4) 4 13 3

Q18.A radioactive sample decays 7 times its original quantity in 15 minutes. The half-life of the sample is 8 (1) 5 min (2) 7. 5 min (3) 15 min (4) 30 min

Q18.Following statements related to radioactivity are given below : (A) Radioactivity is a random and spontaneous process and is dependent on physical and chemical conditions. (B) The number of undecayed nuclei in the radioactive sample decays exponentially with time. (C) Slope of the graph of loge (no. of undecayed nuclei) vs. time represents the reciprocal of mean life time (τ) . 1 (D) Product of decay constant (λ) and half-life time (T 2 ) is not constant. Choose the most appropriate answer from the options given below: (1) (A) and (B) only (2) (B) and (D) only (3) (B) and (C) only (4) (C) and (D) only

Q18.What is the half-life period of a radioactive material if its activity drops to 1 of its initial value of 30 years ? 16th (1) 9. 5 years (2) 8. 5 years (3) 7. 5 years (4) 10. 5 years JEE Main 2022 (27 Jul Shift 1) JEE Main Previous Year Paper

Q18.The ratio of wavelengths of proton and deuteron accelerated by potential Vp and Vd is 1 : √2 . Then, the ratio of Vp to Vd will be (1) 1 : 1 (2) √2 : 1 (3) 2 : 1 (4) 4 : 1

Q18.Find the modulation index of an AM wave having 8 V variation where maximum amplitude of the AM wave is 9 V . (1) 0. 8 (2) 0. 5 (3) 0. 2 (4) 0. 1 JEE Main 2022 (29 Jul Shift 1) JEE Main Previous Year Paper

Q18.An unpolarised light beam of intensity 2𝐼0 is passed through a polaroid 𝑃 and then through another polaroid 𝑄 which is oriented in such a way that its passing axis makes an angle of 30° relative to that of 𝑃. The intensity of the emergent light is (1) 𝐼0 (2) 𝐼0 4 2 3𝐼0 3𝐼0 (3) (4) 4 2 JEE Main 2022 (29 Jul Shift 2) JEE Main Previous Year Paper

Q18.The half life period of a radioactive substance is 60 days. The time taken for 7 th of its original mass to 8 disintegrate will be : (1) 120 days (2) 130 days (3) 180 days (4) 20 days

Q18.Choose the correct option from the following options given below : (1) In the ground state of Rutherford's model (2) An atom has a nearly continuous mass electrons are in stable equilibrium. While in distribution in a Rutherford's model but has a Thomson's model electrons always experience a highly non-uniform mass distribution in net-force. Thomson's model (3) A classical atom based on Rutherford's model is (4) The positively charged part of the atom possesses doomed to collapse. most of the mass in Rutherford's model but not in Thomson's model.

Q18.The ratio for the speed of the electron in the 3rd orbit of He+ to the speed of the electron in the 3rd orbit of hydrogen atom will be : (1) 1: 1 (2) 1: 2 (3) 4: 1 (4) 2: 1

Q18.An α particle and a carbon 12 atom has same kinetic energy K . The ratio of their de-Broglie wavelengths (λα : λC12) is (1) √3 : 1 (2) 1 : √3 (3) 2 : √3 (4) 3 : 1

Q18.A radioactive nucleus can decay by two different processes. Half-life for the first process is 3. 0 hours while it is 4. 5 hours for the second process. The effective halflife of the nucleus will be (1) 3. 75 hours (2) 0. 56 hours (3) 0. 26 hours (4) 1. 80 hours

Q19.The light of two different frequencies whose photons have energies 3. 8 eV and 1. 4 eV respectively, illuminate a metallic surface whose work function is 0. 6 eV successively. The ratio of maximum speeds of emitted electrons for the two frequencies respectively will be : (1) 2 : 1 (2) 4 : 1 (3) 1 : 2 (4) 1 : 4

Q19.An 𝛼 particle and a proton are accelerated from rest through the same potential difference. The ratio of linear momenta acquired by above two particals will be : (1) √2: 1 (2) 2√2: 1 (3) 4√2: 1 (4) 8: 1

Q19.Hydrogen atom from excited state comes to the ground by emitting a photon of wavelength λ. The value of principal quantum number n of the excited state will be : ( R : Rydberg constant) (1) √λRλ−1 (2) √ λR−1λR (3) √ λR−1λ (4) √λR2λR−1

Q19.In the following nuclear reaction, β− γ D α→D1 →D2 α→D3 →D4 Mass number of D is 182 and atomic number is 74 . Mass number and atomic number of D4 respectively will be (1) 174 and 71 (2) 174 and 69 (3) 172 and 69 (4) 172 and 71