Practice Questions

Q17.A vessel of depth 2h is half filled with a liquid of refractive index 2√2 and the upper half with another liquid of refractive index √2 . The liquids are immiscible. The apparent depth of the inner surface of the bottom of the vessel will be JEE Main 2020 (09 Jan Shift 1) JEE Main Previous Year Paper (1) h (2) h √2 2(√2+1) (3) h (4) 3√2h 3√2 4

Q17.An electron, a doubly ionized helium ion ( He++ ) and proton are having the same kinetic energy. The relation between their respective de-Broglie wavelength λe*λHe++ and λp is : (1) λe > λHe++ > λp (2) λe < λHe++ == λp (3) λe > λp > λHe++ (4) λe < λp < λHe++

Q18.Interference fringes are observed on a screen by illuminating two thin slits 1 mm apart with a light source (λ = 632. 8 nm). The distance between the screen and the slits is 100 cm. If a bright fringe is observed on a screen at distance of 1. 27 mm from the central bright fringe, then the path difference between the waves, which are reaching this point from the slits is close to : (1) 1. 27μm (2) 2 . 87 nm (3) 2 nm (4) 2. 05 μm

Q18.In a double – slit experiment, at a certain point on the screen the path difference between the two interfering waves is 1 8 th of a wavelength. The ratio of the intensity of light at that point to that at the center of a bright fringe is: (1) 0.853 (2) 0.672 (3) 0.568 (4) 0.760 →

Q18.In a Young’s double slit experiment, the separation between the slits is 0.15mm . In the experiment, a source of light of wavelength 589nm is used and the interference pattern is observed on a screen kept 1.5m away. The separation between the successive bright fringes on the screen is: (1) 6.9mm (2) 3.9mm (3) 5.9mm (4) 4.9mm

Q19.An amplitude modulated waves is represented by expression vm = 5(1 + 0. 6 cos 6280t) sin(211 × 104t) V. The minimum and maximum amplitudes of the amplitudes modulated wave are, respectively: (1) 2 3 V, 5V (2) 52 V, 8V (3) 5V, 8V (4) 3V, 5V

Q19.When a diode is forward biased, it has a voltage drop of 0. 5 V . the safe limit of current through the diode is 10 mA . If a battery of emf 1. 5 V is used in the circuit, the value of minimum resistance to be connected in series with the diode so that the current does not exceed the safe limit is : (1) 300 Ω (2) 50 Ω (3) 100 Ω (4) 200 Ω

Q19.A radioactive nucleus decays by two different processes. The half-life for the first process is 10 s and that for the second is 100 s. The effective half-life of the nucleus is close to: (1) 9 s (2) 6 s (3) 55 s (4) 12 s

Q19.A particle moving with kinetic energy E has de Broglie wavelength λ . If energy ΔE is added to its energy, the wavelength become λ . Value of ΔE, is: 2 (1) E (2) 4E (3) 3E (4) 2E

Q20.Using screw gauge of pitch 0. 1 cm and 50 divisions on its circular scale, the thickness of an object is measured. It should correctly be recorded as, (1) 2. 121 cm (2) 2. 124 cm (3) 2. 125 cm (4) 2. 123 cm

Q20.If the screw on a screw-gauge is given six rotations, it moves by 3mm on the main scale. If there are 50 divisions on the circular scale the least count of the screw gauge is: (1) 0.001cm (2) 0.02m (3) 0.01cm (4) 0.001mm

Q20.If a semiconductor photo diode can detect a photon with a maximum wavelength of 400 nm, then its band gap energy is: Planck's constant h = 6. 63 × 10−34 J. s Speed of light c = 3 × 108 m s−1 (1) 1. 1 eV (2) 2. 0 eV (3) 1. 5 eV (4) 3. 1 eV

Q20.Identify the operation performed by the circuit given below : (1) NAND (2) OR (3) AND (4) NOT

Q20.In the given circuit, value of Y is: (1) 0 (2) toggles between 0 and 1 (3) will not execute (4) 1 JEE Main 2020 (08 Jan Shift 2) JEE Main Previous Year Paper

Q20.Boolean relation at the output stage- Y for the following circuit is: (1) − − (2) A + B A + B (3) A ∙B (4) − − A ∙ B

Q20.In the following, digital circuit, what will be the output a ' Z', when the input (A, B) are (1, 0), (0, 0), (1, 1), (0, 1) (1) 0, 0, 1, 0 (2) 1, 0, 1, 1 (3) 1, 1, 0, 1 (4) 0, 1, 0, 0

Q26.The number of subshells associated with n = 4 and m = −2 quantum numbers is: (1) 8 (2) 2 (3) 16 (4) 4

Q26.Preparation of Bakelite proceeds via reactions: (1) Electrophilic addition and dehydration (2) Condensation and elimination (3) Electrophilic substitution and dehydration (4) Nucleophilic addition and dehydration

Q26.The de Broglie wavelength of an electron in the 4th Bohr orbit is: (1) 2πa0 (2) 4πa0 (3) 6πa0 (4) 8πa0

Q26.The region in the electromagnetic spectrum where the Balmer series lines appear is: (1) Visible (2) Microwave (3) Infrared (4) Ultraviolet

Q26.The difference between the radii of 3rd and 4th orbits of L2+i is ΔR1 . The difference between the radii of 3rd and 4th orbits of He+ ΔR2. Ratio ΔR1 : ΔR2 is : (1) 8 : 3 (2) 3 : 8 (3) 2 : 3 (4) 3 : 2

Q26.The atomic number of the element unnilennium is : (1) 109 (2) 102 (3) 108 (4) 119

Q27.In general, the property (magnitudes only) that shows an opposite trend in comparison to other properties across a period is : (1) lonization enthalpy (2) Electronegativity (3) Electron gain enthalpy (4) Atomic radius

Q27.The correct order of the ionic radii of O2−, N3−, F−, Mg2+, Na+ and Al3+ is : (1) N3−< O2−< F−< Na+ < Mg2* < AI3+ (2) AI3+ < Na+ < Mg2+ < O2−< F−< N3− (3) Al3+ < Mg2+ < Na+ < F−< O2−< N3− (4) N3−< F−< O2−< Mg2+ < Na+ < AI3+

Q27.The process that is NOT endothermic in nature is : (1) Ar(g) + e−→Ar−(g) (2) H(g) + e−→H−(g) (3) O− + e−→O2− (g) (g) (4) Na(g) →Na+(g) + e−