Practice Questions

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

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.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 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.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.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.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.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 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.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.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.

Q27.The wavelength of the radiation emitted is λ0 when an electron jumps from the second excited state to the first excited state of hydrogen atom. If the electron jumps from the third excited state to the second orbit of the hydrogen atom, the wavelength of the radiation emitted will be 20 x λ0 . The value of x is________.

Q27.The ratio of wavelength of spectral lines Hα and Hβ in the Balmer series is 20x . The value of x is _____.

Q27.Two identical cells, when connected either in parallel or in series gives same current in an external resistance 5 Ω. The internal resistance of each cell will be ______ Ω.

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.In an experiment for estimating the value of focal length of converging mirror, image of an object placed at 40 cm from the pole of the mirror is formed at distance 120 cm from the pole of the mirror. These distances are measured with a modified scale in which there are 20 small divisions in 1 cm. The value of error in 1 measurement of focal length of the mirror is cm. The value of 𝐾 is ______. 𝐾

Q27.An object is placed on the principal axis of convex lens of focal length 10 cm as shown. A plane mirror is placed on the other side of lens at a distance of 20 cm. The image produced by the plane mirror is 5 cm inside the mirror. The distance of the object from the lens is ____ cm.

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

Q27.An electron in a hydrogen atom revolves around its nucleus with a speed of 6. 76 × 106 m s–1 in an orbit of radius 0. 52 Å. The magnetic field produced at the nucleus of the hydrogen atom is _______ T.

Q27.A straight wire AB of mass 40 g and length 50 cm is suspended by a pair of flexible leads in uniform magnetic field of magnitude 0 . 40 T as shown in the figure. The magnitude of the current required in the wire to remove the tension in the supporting leads is _____ A. (Take 𝑔= 10 m s-2.

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 beam of light consisting of two wavelengths 7000 A and 5500 A is used to obtain interference pattern in Young's double slit experiment. The distance between the slits is 2. 5 mm and the distance between the plane of slits and the screen is 150 cm. The least distance from the central fringe, where the bright fringes due to both the wavelengths coincide, is n × 10–5 m. The value of n is _____.

Q27.Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R Assertion A : The nuclear density of nuclides 105B, 63Li, 5626Fe, 2010Ne and 20983Bi can be arranged as ρNBi > ρNFe > ρNNe > ρNB > ρNLi Reason R : The radius R of nucleus is related to its mass number A as R = R0 A 1 3 , where R0 is a constant. In the light of the above statement, choose the correct answer from the options given below : (1) Both A and R are true and R is the correct (2) A is false but R is true explanation of A (3) A is true but R is false (4) Both A and R are true but R is NOT the correct explanation of A