Practice Questions

Q25.Two equal positive point charges are separated by a distance 2𝑎. The distance of a point from the centre of the line joining two charges on the equatorial line (perpendicular bisector) at which force experienced by a test charge becomes maximum is 𝑎 The value of 𝑥 is ______. 𝑞0 √𝑥. JEE Main 2023 (01 Feb Shift 1) JEE Main Previous Year Paper

Q25.Unpolarised light is incident on the boundary between two dielectric media, whose dielectric constants are 2. 8 (medium – 1) and 6. 8 (medium – 2), respectively. To satisfy the condition, so that the reflected and refracted 1 rays are perpendicular to each other, the angle of incidence should be tan−1 (1 + 10θ ) 2 , the value of θ is ______. (Given for dielectric media, μr = 1 )

Q26.Electron beam used in an electron microscope, when accelerated by a voltage of 20 kV has a de-Broglie wavelength of λ0 . If the voltage is increased to 40 kV then the de-Broglie wavelength associated with the electron beam would be: (1) 3λ0 (2) 9λ0 (3) λ0 (4) λ0 2 √2

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.Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R Assertion A: The phase difference of two light waves change if they travel through different media having same thickness, but different indices of refraction. Reason R: The wavelengths of waves are different in different media. In the light of the above statements, choose the most appropriate answer from the options given below (1) Both A and R are correct but R is NOT the (2) A is not correct but R is correct correct explanation of A (3) A is correct but R is not correct (4) Both A and R are correct and R is the correct explanation of A o o

Q26.The light rays from an object have been reflected towards an observer from a standard flat mirror, the image observed by the observer are :- A. Real B. Erect C. Smaller in size than object D. Laterally inverted Choose the most appropriate answer from the options given below: (1) B and D only (2) B and C only (3) A and D only (4) A, C and D only

Q26.A parallel plate capacitor with plate area 𝐴 and plate separation 𝑑 is filled with a dielectric material of dielectric constant 𝐾= 4 . The thickness of the dielectric material is 𝑥, where 𝑥< 𝑑. 2𝑑 𝑥= , respectively. If 𝐶1 = 2 μF, the value Let 𝐶1 and 𝐶2 be the capacitance of the system for 𝑥= 13𝑑 and 3 of 𝐶2 is _____ μF .

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

Q26.If a radioactive element having half-life of 30 min is undergoing beta decay, the fraction of radioactive element remains undecayed after 90 min will be : (1) 1 (2) 1 8 16 (3) 1 (4) 1 4 2

Q26.A stream of a positively charged particles having 𝑚= 2 × 1011 C kg-1 and velocity →v0 = 3 × 107 ^𝑖 m s-1 is deflected by an electric field 1 . 8 ^𝑗 kV m-1. The electric field exists in a region of 10 cm along 𝑥 direction. Due to the electric field, the deflection of the charge particles in the 𝑦 direction is _____ mm.

Q26.A rectangular parallelopiped is measured as 1 cm × 1 cm × 100 cm. If its specific resistance is 3 × 10-7Ω m, then the resistance between its two opposite rectangular faces will be _____ × 10-7Ω.

Q26.The radius of 2nd orbit of He+ of Bohr's model is r1 and that of fourth orbit of Be3+ is represented as r2. Now the ratio r2 is x : 1. The value of x is _____. r1 Q27. 238 92 A →23490 B + 42D + Q In the given nuclear reaction, the approximate amount of energy released will be: [Given, mass of 238 92 A = 238. 05079 × 931. 5 MeV c−2 , mass of 23490B = 234. 04363 × 931. 5 MeV c−2 , mass of 42D = 4. 00260 × 931. 5 Me V c−2 ] (1) 3. 82 MeV (2) 5. 9 MeV (3) 2. 12 MeV (4) 4. 25 MeV

Q26.As shown in the figure, a plane mirror is fixed at a height of 50 cm from the bottom of tank containing water (μ = 43 ). The height of water in the tank is 8 cm. A small bulb is placed at the bottom of the water tank. The distance of image of the bulb formed by mirror from the bottom of the tank is ______ cm.

Q26.A network of four resistances is connected to 9 V battery, as shown in figure. The magnitude of voltage difference between the points A and B is __________ V.

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.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.Proton (P) and electron (e) will have same de-Broglie wavelength when the ratio of their momentum is (assume, mp = 1849 me ) (1) 1 : 1 (2) 1 : 1849 (3) 1 : 43 (4) 43 : 1

Q26.Expression for an electric field is given by →𝐸= 4000 𝑥2 ^i V m-1. The electric flux through the cube of side 20 cm when placed in electric field (as shown in the figure) is ______ V cm. JEE Main 2023 (31 Jan Shift 1) JEE Main Previous Year Paper

Q26.In an experiment to find emf of a cell using potentiometer, the length of null point for a cell of emf 1 . 5 V is found to be 60 cm. If this cell is replaced by another cell of emf 𝐸. the length-of null point increases by 𝑥 40 cm. The value of 𝐸 is V. The value of 𝑥 is ______. 10

Q26.As per the given figure, if d𝑡=d𝐼

Q26.In the circuit shown, the energy stored in the capacitor is 𝑛 μJ. The value of 𝑛 is _____.

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.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.As shown in the figure, a configuration of two equal point charges 𝑞0 = + 2𝜇C is placed on an inclined plane. Mass of each point charge is 20 g. Assume that there is no friction between charge and plane. For the system of two point charges to be in equilibrium (at rest) the height ℎ= 𝑥× 10-3 m. The value of 𝑥 is 1 Take = 9 × 109 N m2 C-2, 𝑔= 10 m s-2 4𝜋𝜀0 𝑥

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