Practice Questions

Q23.A plane electromagnetic wave travels in free space along the x-direction. The electric field component of the wave at a particular point of space and time is E = 6 V m-1 along y-direction. Its corresponding magnetic field component, B would be: (1) 2 × 10-8 T along z- (2) 2 × 10-8 T along y- (3) 6 × 10-8 T along z- (4) 6 × 10-8 T along x- direction direction direction direction

Q23.An electromagnetic wave is represented by the electric filed →E = E0^nsin⁡ωt + 6𝑦- 8𝑧. Taking unit vectors in 𝑥, 𝑦 and 𝑧 directions to be ^𝑖, ^𝑗, ^𝑘, the directions of propogations ^s, is: (1) 3^𝑖- 4^𝑗 (2) -3^𝑖+ 4^𝑗 ^s = ^s = 5 5 4^𝑖- 3^𝑘 -4^𝑖- 3^𝑘 (3) (4) ^s = ^s = 5 5

Q23.The total number of turns and cross-section area in a solenoid is fixed. However, its length L is varied by adjusting the separation between windings. The inductance of solenoid will be proportional to: (1) L (2) 1 L2 (3) 1 (4) L2 L JEE Main 2019 (09 Apr Shift 1) JEE Main Previous Year Paper →

Q24.A monochromatic light is incident at a certain angle on an equilateral triangular prism and suffers minimum deviation. If the refractive index of the material of the prism is √3, then the angle of incidence is : (1) 90∘ (2) 30∘ (3) 60∘ (4) 45∘

Q25.The value of numerical aperture of the objective lens of a microscope is 1.25 . If light of wavelength 5000 Å is used, the minimum separation between two points, to be seen as distinct, will be: (1) 0.48 μm (2) 0.24 μm (3) 0.38 μm (4) 0.12 μm

Q25.A plane electromagnetic wave of frequency 50 𝑀𝐻𝑧 travels in free space along the positive 𝑥 - direction. At a particular point in space and time, →𝐸= 6.3 ^𝑗 𝑉/ 𝑚, The corresponding magnetic field →𝐵, at that point will be: (1) 2.1 × 10-8^𝑘 𝑇 (2) 18.9 × 108^𝑘 𝑇 (3) 18.9 × 10-8^𝑘 𝑇 (4) 6.3 × 10-8^𝑘 𝑇

Q25.The eye can be regarded as a single refracting surface. The radius of curvature of this surface is equal to that of the cornea (7 .8 mm). This surface separates two media of refractive indices 1 and 1.34 . Calculate the distance from the refracting surface at which a parallel beam of light will come to focus. JEE Main 2019 (10 Jan Shift 2) JEE Main Previous Year Paper (1) 4 .0 cm (2) 1 cm (3) 2 cm (4) 3.07 cm

Q25.Calculate the limit of resolution of a telescope objective having a diameter of 200 cm , if it has to detect light of wavelength 500 nm coming from a star. (1) 305 × 10-9 radian (2) 610 × 10-9 radian (3) 152.5 × 10-9 radian (4) 457.5 × 10-9 radian

Q26.Diameter of the objective lens of a telescope is 250 cm. For light of wavelength 600 nm coming from a distant object, the limit of resolution of the telescope is close to: (1) 1.5 × 10−7 rad (2) 3.0 × 10−7 rad (3) 2.0 × 10−7 rad (4) 4.5 × 10−7 rad

Q26.In a photoelectric effect experiment, the threshold wavelength of light is 380 nm . If the wavelength of incident light is 260 nm , the maximum kinetic energy of emitted electrons will be Given E (in eV ) = 1237 λ(in nm) (1) 4.5 eV (2) 3.0 eV (3) 1.5 eV (4) 15.1 eV

Q27.In a radioactive decay chain, the initial nucleus is 232 90 Th. At the end, there are 6 α-particles and 4β-particles which are emitted. If the end nucleus is AZX, A and Z are given by: (1) A = 208; Z = 82 (2) A = 208; Z = 80 (3) A = 200; Z = 81 (4) A = 202; Z = 80

Q27.A 2 mW laser operates at a wavelength of 500 nm . The number of photons that will be emitted per second is: [Given Planck's constant h = 6.6 × 10-34 J s, speed of light c = 3.0 × 108 m / s ] (1) 1.5 × 1016 (2) 5 × 1015 (3) 2 × 1016 (4) 1 × 1016 JEE Main 2019 (10 Apr Shift 2) JEE Main Previous Year Paper

Q27.The output of the given logic circuit is: (1) − (2) − A B A B ¯(3) AB + AB (4) − − A B + A B

Q28.To get output '1' at R, for the given logic gate circuit the input values must be: (1) X = 1, Y = 1 (2) X = 0, Y = 0 (3) X = 0, Y = 1 (4) X = 1, Y = 0

Q28.A He+ ion is in its first excited state. Its ionization energy is: (1) 13.60 eV (2) 48.36 eV (3) 54.40 eV (4) 6.04 eV

Q28.A 100V carrier wave is made to vary between 160 V and 40 V by a modulating signal. What is the modulation index? (1) 0.3 (2) 0.6 (3) 0.4 (4) 0.5

Q29.The truth table for the circuit given in the figure is: (1) A B Y (2) A B Y 0 0 0 0 0 1 0 1 0 0 1 0 1 0 1 1 0 0 1 1 1 1 1 0 (3) A B Y (4) A B Y 0 0 1 0 0 1 0 1 1 0 1 1 1 0 1 1 0 0 1 1 1 1 1 0

Q29.The least count of the main scale of a screw gauge is 1 mm. The minimum number of divisions on its circular scale required to measure 5 μm diameter of a wire is: (1) 50 (2) 100 (3) 500 (4) 200

Q30.The wavelength of the carrier waves in a modern optical fiber communication network is close to: (1) 2400 nm (2) 900 nm (3) 600 nm (4) 1500 nm

Q30.The physical sizes of the transmitter and receiver antenna in a communication system are: (1) proportional to carrier frequency (2) independent of both carrier and modulation frequency (3) inversely proportional to modulation frequency (4) inversely proportional to carrier frequency

Q30.A signal Acosωt is transmitted using ν0sinω0t as carrier wave. The correct amplitude modulated (AM) signal is: JEE Main 2019 (09 Apr Shift 1) JEE Main Previous Year Paper (1) ν0sin[ω0(1 + 0.01Asinωt)t] (2) (ν0 + A)cosωt sinω0t (3) ν0 sinω0t + Acosωt (4) ν0sinω0t + A2 sin(ω0 −ω)t + A2 sin(ω0 + ω)t

Q31.What would be the molality of 20% (mass/mass) aqueous solution of KI ? (molar mass of KI = 166 g mol−1 ) (1) 1.35 (2) 1.51 (3) 1.08 (4) 1.48

Q31.The percentage composition of carbon by mole in methane is: (1) 75 % (2) 20 % (3) 80 % (4) 25 % Q32.0.27 g of a long chain fatty acid was dissolved in 100 cm3 of hexane. 10 mL of this solution was added dropwise to the surface of water in a round watch glass. Hexane evaporates and a monolayer is formed. The distance from edge to centre of the watch glass is 10 cm . What is the height of the monolayer? [Density of fatty acid = 0.9 g cm-3; π = 3] (1) 10-4 m (2) 10-6 m (3) 10-8 m (4) 10-2 m

Q32.The type of hybridization and no. of lone pair(s) of electron of Xe in XeOF4 , respectively, are: (1) sp3d2 and 1 (2) sp3d2 and 2 (3) sp3d and 2 (4) sp3d and 1

Q32.The element with Z = 120 (not yet discovered) will be a/an (1) transition metal. (2) alkaline earth metal. (3) alkali metal. (4) inner-transition metal.