Practice Questions

Q21.For a moving coil galvanometer, the deflection in the coil is 0. 05 rad when a current of 10 mA is passed through it. If the torsional constant of suspension wire is 4. 0 × 10–5 N m rad−1 , the magnetic field is 0. 01 T and the number of turns in the coil is 200 , the area of each turn (in cm2 ) is : (1) 2. 0 (2) 1. 0 (3) 1. 5 (4) 0. 5

Q21.As shown in the figure, a long straight conductor with semicircular arc of radius π m is carrying current 10 I = 3A . The magnitude of the magnetic field. at the center O of the arc is: (The permeability of the vacuum = 4π × 10−7 NA−2 ) (1) 6 μT (2) 1 μT (3) 4 μT (4) 3 μT

Q21.The speed of a swimmer is 4 km h-1 in still water. If the swimmer makes his strokes normal to the flow of river of width 1 km, he reaches a point 750 m down the stream on the opposite bank. The speed of the river water is ______ km h-1.

Q22.Which of the following Maxwell’s equation is valid for time varying conditions but not valid for static conditions: → → → → (1) (2) ∮ B ⋅ dl = μ0I ∮ E ⋅ dl = 0 −→ → → (3) ∮→D ⋅dA = Q (4) ∮ E ⋅dl = −∂ϕB∂t

Q23.A thin prism P1 with an angle 6° and made of glass of refractive index 1. 54 is combined with another prism P2 made from glass of refractive index 1. 72 to produce dispersion without average deviation. The angle of prism P2 is : (1) 6° (2) 1. 3° (3) 7. 8° (4) 4. 5°

Q23.In a Young’s double slit experiment, two slits are illuminated with a light of wavelength 800 nm . The line joining A1P is perpendicular to A1A2 as shown in the figure. If the first minimum is detected at P , the value of slits separation a will be : JEE Main 2023 (29 Jan Shift 1) JEE Main Previous Year Paper The distance of screen from slits D = 5 cm . (1) 0. 4 mm (2) 0. 5 mm (3) 0. 2 mm (4) 0. 1 mm

Q24.An ice cube has a bubble inside. When viewed from one side the apparent distance of the bubble is 12 cm . When viewed from the opposite side, the apparent distance of the bubble is observed as 4 cm . If the side of the ice cube is 24 cm , the refractive index of the ice cube is (1) 3 (2) 2 2 3 (3) 6 (4) 4 5 3

Q24.A scientist is observing a bacteria through a compound microscope. For better analysis and to improve its resolving power he should. (Select the best option) (1) Increase the wave length of the light (2) Increase the refractive index of the medium between the object and objective lens (3) Decrease the focal length of the eye piece (4) Decrease the diameter of the objective lens

Q24.A plane electromagnetic wave of frequency 20 MHz propagates in free space along x-direction. At a particular → → space and time E = 6. 6ˆj V m−1 . What is B at this point? (1) 2. 2 × 10−8ˆkT (2) −2. 2 × 10−8ˆiT (3) −2. 2 × 10−8ˆkT (4) 2. 2 × 10−8ˆi T

Q24.Two objects A and B are placed at 15 cm and 25 cm from the pole in front of a concave mirror having radius of curvature 40 cm . The distance between images formed by the mirror is: (1) 40 cm (2) 60 cm (3) 160 cm (4) 100 cm

Q24.A microscope is focused on an object at the bottom of a bucket. If liquid with refractive index 5 is poured 3 inside the bucket, then microscope have to be raised by 30 cm to focus the object again. The height of the liquid in the bucket is : (1) 75 cm (2) 50 cm (3) 18 cm (4) 12 cm

Q25.In Young's double slits experiment, the position of 5th bright fringe from the central maximum is 5 cm . The distance between slits and screen is 1 m and wavelength of used monochromatic light is 600 nm . The separation between the slits is: (1) 60 μm (2) 48 μm (3) 12 μm (4) 36 μm

Q25.A point source of 100 W emits light with 5% efficiency. At a distance of 5 m from the source, the intensity produced by the electric field component is: (1) 1 W (2) 1 W 2π m2 40π m2 1 (3) 10π m2 W (4) 201 m2W

Q25.A 2 meter long scale with least count of 0. 2 cm is used to measure the locations of objects on an optical bench. While measuring the focal length of a convex lens, the object pin and the convex lens are placed at 80 cm mark and 1 m mark, respectively. The image of the object pin on the other side of lens coincides with image pin that is kept at 180 cm mark. The % error in the estimation of focal length is: JEE Main 2023 (06 Apr Shift 2) JEE Main Previous Year Paper (1) 0. 85 (2) 1. 70 (3) 1. 02 (4) 0. 51

Q26.An α particle, a proton and an electron have the same kinetic energy. Which one of the following is correct in case of their de-Broglie wavelength: (1) λα > λp > λe (2) λα < λp < λe (3) λα = λp = λe (4) λα > λp < λe

Q26.The ratio of de-Broglie wavelength of an α -particle and a proton accelerated from rest by the same potential is 1 , the value of m is: √m JEE Main 2023 (29 Jan Shift 2) JEE Main Previous Year Paper (1) 4 (2) 16 (3) 8 (4) 2

Q26.In photoelectric effect A. The photocurrent is proportional to the intensity of the incident radiation. B. Maximum kinetic energy with which photoelectrons are emitted depends on the intensity of incident light. C. Max K.E. with which photoelectrons are emitted depends on the frequency of incident light. D. The emission of photoelectrons require a minimum threshold intensity of incident radiation. E. Max K.E. of the photoelectrons is independent of the frequency of the incident light. Choose the correct answer from the options given below: (1) A and B only (2) A and E only (3) A and C only (4) B and C only

Q26.An electron accelerated through a potential difference V1 has a de-Broglie wavelength of λ. When the potential is changed to V2 , its de-Broglie wavelength increases by 50%. The value of ( V1V2 ) is equal to : JEE Main 2023 (30 Jan Shift 2) JEE Main Previous Year Paper (1) 3 (2) 49 (3) 3 (4) 4 2

Q26.If the two metals A and B are exposed to radiation of wavelength 350 nm. The work functions of metals A and B are 4. 8 eV and 2. 2 eV . Then choose the correct option (1) Metal B will not emit photo-electrons (2) Both metals A and B will emit photo-electrons (3) Both metals A and B will not emit (4) Metal A will not emit photo-electrons photoelectrons

Q26.A proton and an α -particle are accelerated from rest by 2 V and 4 V potentials, respectively. The ratio of their de-Broglie wavelength is : (1) 8 : 1 (2) 2 : 1 (3) 4 : 1 (4) 16 : 1

Q26.The threshold frequency of metal is f0 . When the light of frequency 2f0 is incident on the metal plate, the maximum velocity of photoelectron is v1 . When the frequency of incident radiation is increased to 5f0 . the maximum velocity of photoelectrons emitted is v2 . The ratio of v1 to v2 is: (1) v1 v2 = 21 (2) v2v1 = 81 (3) v1 v2 = 161 (4) v2v1 = 41

Q27.The ratio of the de-Broglie wavelengths of proton and electron having same kinetic energy: (Assume mp = me × 1849 ) (1) 1 : 43 (2) 1 : 30 (3) 1 : 62 (4) 2 : 43

Q27.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 21 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 × 1024 (2) 6. 76 × 1024 (3) 6. 76 × 1023 (4) 1. 69 × 1024

Q27.A 12. 5 eV electron beam is used to bombard gaseous hydrogen at room temperature. The number of spectral lines emitted will be: (1) 1 (2) 4 (3) 2 (4) 3

Q27.A photon is emitted in transition from n = 4 to n = 1 level in hydrogen atom. The corresponding wavelength for this transition is (given, h = 4 × 10−15 eV s ) (1) 941 nm (2) 974 nm (3) 99. 3 nm (4) 94. 1 nm