Practice Questions

Q16.The focal length 𝑓 is related to the radius of curvature 𝑟 of the spherical convex mirror by: 1 1 (1) 𝑓= - 2𝑟 (2) 𝑓= + 2𝑟 (3) 𝑓= 𝑟 (4) 𝑓= - 𝑟

Q16.The magnetic susceptibility of a material of a rod is 499. Permeability in vacuum is 4π × 10−7 Hm−1. Absolute permeability of the material of the rod is (1) 4π × 10−4 Hm−1 (2) 2π × 10−4 Hm−1 (3) 3π × 10−4 Hm−1 (4) π × 10−4 Hm−1 JEE Main 2021 (20 Jul Shift 2) JEE Main Previous Year Paper

Q16.Region I and II are separated by a spherical surface of radius 25 cm. An object is kept in region I at a distance of 40 cm from the surface. The distance of the image from the surface is: (1) 55. 44 cm (2) 9. 52 cm (3) 18. 23 cm (4) 37. 58 cm

Q16.An α particle and a proton are accelerated from rest by a potential difference of 200 V . After this, their de Broglie wavelengths are λα and λp respectively. The ratio λαλp is : (1) 8 (2) 3. 8 (3) 2. 8 (4) 7. 8

Q17.A particular hydrogen like ion emits radiation of frequency 2. 92 × 1015 Hz when it makes transition from n = 3 to n = 1. The frequency in Hz of radiation emitted in transition from n = 2 to n = 1 will be: (1) 6. 57 × 1015 (2) 2. 46 × 1015 (3) 0. 44 × 1015 (4) 4. 38 × 1015

Q17.In a Young's double slit experiment, the width of the one of the slit is three times the other slit. The amplitude of the light coming from a slit is proportional to the slit-width. Find the ratio of the maximum to the minimum intensity in the interference pattern. JEE Main 2021 (24 Feb Shift 1) JEE Main Previous Year Paper (1) 1: 4 (2) 2: 1 (3) 3: 1 (4) 4: 1

Q17.The wavelength of the photon emitted by a hydrogen atom when an electron makes a transition from n = 2 to n = 1 state is: (1) 121. 8 nm (2) 194. 8 nm (3) 490. 7 nm (4) 913. 3 nm JEE Main 2021 (25 Feb Shift 2) JEE Main Previous Year Paper

Q17.An electron of mass me and a proton of mass mP are accelerated through the same potential difference. The ratio of the de-Broglie wavelength associated with the electron to that with the proton is (1) mP (2) 1 me mp (3) √mpme (4) me

Q17.Some nuclei of a radioactive material are undergoing radioactive decay. The time gap between the instances when a quarter of the nuclei have decayed and when half of the nuclei have decayed is given as: (where 𝜆 is the decay constant) JEE Main 2021 (25 Jul Shift 1) JEE Main Previous Year Paper (1) 1 𝑙n2 (2) 𝑙𝑛2 2 𝜆 𝜆 (3) 2𝑙n2 (4) 𝑙n32 𝜆 𝜆

Q17.For a series LCR circuit with R = 100 Ω, L = 0. 5 mH and C = 0. 1 pF connected across 220 V −50 Hz AC supply, the phase angle between current and supplied voltage and the nature of the circuit is: (1) 0°, resistive circuit (2) ≈90°, predominantly inductive circuit (3) 0°, resonance circuit (4) ≈90°, predominantly capacitive circuit →

Q17.There are two infinitely long straight current-carrying conductors and they are held at right angles to each other so that their common ends meet at the origin as shown in the figure given below. The ratio of current in both conductors is 1: 1. The magnetic field at point 𝑃 is_________ . (1) 𝜇0I + 𝑦2 - (𝑥+ 𝑦) (2) 𝜇0I𝑥𝑦 √𝑥2 + 𝑦2 - (𝑥+ 𝑦) 4πxy√𝑥2 4π (3) 𝜇0I + 𝑦2 + (𝑥+ 𝑦) (4) 𝜇0I𝑥𝑦 √𝑥2 + 𝑦2 + (𝑥+ 𝑦) 4πxy√𝑥2 4π

Q17.The light waves from two coherent sources have same intensity I1 = I2 = I0. In interference pattern the intensity of light at minima is zero. What will be the intensity of light at maxima? (1) I0 (2) 2I0 (3) 4I0 (4) 5I0

Q17.Find the distance of the image from object O, formed by the combination of lenses in the figure: JEE Main 2021 (27 Aug Shift 1) JEE Main Previous Year Paper (1) 75 cm (2) 10 cm (3) infinity (4) 20 cm

Q17.For an electromagnetic wave travelling in free space, the relation between average energy densities due to electric (Ue) and magnetic (Um) fields is : (1) Ue = Um (2) Ue > Um (3) Ue < Um (4) Ue ≠Um

Q17.The incident ray, reflected ray and the outward drawn normal are denoted by the unitvectors →a, band →c respectively. Then choose the correct relation for these vectors. → → (1) (2) b =→a+ 2→c b = 2→a+→c → → (3) (4) b =→a−→c b =→a−2(→a⋅→c)→c

Q17.A short straight object of height 100 cm lies before the central axis of a spherical mirror whose focal length has absolute value |f| = 40 cm . The image of object produced by the mirror is of height 25 cm and has the same orientation of the object. One may conclude from the information: (1) Image is real, same side of convex mirror. (2) Image is virtual, opposite side of concave mirror. (3) Image is real, same side of concave mirror. (4) Image is virtual, opposite side of convex mirror.

Q17.If an electron is moving in the nth orbit of the hydrogen atom, then its velocity (vn) for the nth orbit is given as: (1) vn ∝n (2) vn ∝1n (3) vn ∝n2 (4) vn ∝ n21

Q17.The de-Broglie wavelength of a particle having kinetic energy E is λ. How much extra energy must be given to this particle so that the de-Broglie wavelength reduces to 75% of the initial value? (1) E (2) 7E 9 (3) 16E (4) E 9 9

Q17.Two identical photocathodes receive the light of frequencies f1 and f2 respectively. If the velocities of the photo-electrons coming out are v1 and v2 respectively, then (1) v21 −v22 = 2mh [f1 −f2] (2) v21 + v22 = 2hm [f1 + f2] (3) 2 h 21 (4) 2 h 21 v1 + v2 = [ m (f1 + f2)] v1 −v2 = [ m (f1 −f2)]

Q17.A prism of refractive index μ and angle of prism A is placed in the position of minimum angle of deviation. If minimum angle of deviation is also A , then in terms of refractive, (1) 2 cos−1( μ2 ) (2) sin−1( μ2 ) (3) (4) cos−1( μ2 ) 2 sin−1(√μ−1 )

Q17.A particle is travelling 4 times as fast as an electron. Assuming the ratio of de-Broglie wavelength of a particle to that of electron is 2 : 1, the mass of the particle is :- (1) 1 times the mass of e− (2) 8 times the mass of e− 16 (3) 16 times the mass of e− (4) 18 times the mass of e−

Q17.A moving proton and electron have the same de-Broglie wavelength. If K and P denote the K. E. and momentum respectively. Then choose the correct option : (1) Kp > Ke and Pp = Pe (2) Kp < Ke and Pp = Pe (3) Kp < Ke and Pp < Pe (4) Kp = Ke and Pp = Pe

Q17.A 0. 07 H inductor and a 12 Ω resistor are connected in series to a 220 V, 50 Hz AC source. The approximate current in the circuit and the phase angle between current and source voltage are respectively. [Take π as 22 7 ] (1) 8. 8 A and tan−1( 116 ) (2) 88 A and tan−1( 116 ) (3) 0. 88 A and tan−1( 116 ) (4) 8. 8 A and tan−1( 116 ) JEE Main 2021 (27 Jul Shift 1) JEE Main Previous Year Paper

Q17.Consider two separate ideal gases of electrons and protons having same number of particles. The temperature of both the gases are same. The ratio of the uncertainty in determining the position of an electron to that of a proton is proportional to: 𝑚𝑝 𝑚𝑝 (1) (2) √ 𝑚𝑒 𝑚𝑒 (3) 𝑚𝑝 32 (4) 𝑚𝑒 √ 𝑚𝑝 𝑚𝑒 JEE Main 2021 (31 Aug Shift 2) JEE Main Previous Year Paper

Q17.Three rays of light, namely red (R), green (G) and blue (B) are incident on the face PQ of a right angled prism PQR as shown in figure. The refractive indices of the material of the prism for red, green and blue wavelength are 1. 27, 1. 42 and 1. 49 respectively. The colour of the ray(s) emerging out of the face PR is : (1) green (2) red (3) blue and green (4) blue