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WBJEE 2014 Solved Physics Question Paper – Part 11

May 16, 2017 19:18 IST

    Find WBJEE 2014 Solved Physics Question Paper – Part 11 in this article. This paper consists of 5 questions (#51 to #55) from WBJEE 2014 Physics paper. Detailed solution of these questions has been provided so that students can match their solutions.

    Importance of Previous Years’ Paper:

    Previous years’ question papers help aspirants in understanding exam pattern, question format, important topics and assessing preparation. It has also been seen that sometimes questions are repeated in WBJEE Exam. So, this paper will certainly boost your confidence.

    51. A glass slab consists of thin u iform layers of progressively decreasing refractive indices RI (see figure) such that the RI of any layer is μ-mΔμ. Here μ and Δμ denote the RI of 0th layer and the difference in RI between any two consecutive layers, respectively. The integer m = 0, 1, 2, 3..... denotes the numbers of the successive layers. A ray of light from the 0th layer enters the 1st layer at an angle of incidence of 30°. After undergoing the mth refraction, the ray emerges parallel to the interface. If μ = 1.5 and Δμ = 0.015, the value of m is

    WBJEE 2014

     (A) 20

    (B) 30

    (C) 40

    (D) 50

    Ans: (D)


    By using Snell’s law:

    WBJEE 2014

    52. The de-Broglie wavelength of an electron is the same as that of a 50 keV X-ray photon. The ratio of the energy of the photon to the kinetic energy of the electron is (the energy equivalent of electron mass is 0.5 MeV)

    (A) 1 : 50

    (B) 1 : 20

    (C) 20 : 1

    (D) 50 : 1

    Ans: (C)


    WBJEE 2014

    53. Three identical square plates rotate about the axes shown in the figure in such a way that their kinetic energies are equal. Each of the rotation axes passes through the centre of the square. Then the ratio of angular speeds ω1 : ω2 : ω3 is

    WBJEE 2014

    (A) 1 : 1: 1
    (B) √2 : √2 : 1

    (C) 1 : √2 : 1

    (D) 1 : 2 : √2

    Ans: (B)


    We know that,

    WBJEE 2014

    54. To determine the composition of a bimetallic alloy, a sample is first weighed in air and then in water. These weights are found to be w1 and w2 respectively. If the densities of the two constituent metals are ρ1 and ρ2 respectively, then the weight of the first metal in the sample is (where ρw is the density of water)

    WBJEE 2014

    Ans: (A)


    WBJEE 2014

    55. Sound waves are passing through two routes-one in straight path and the other along a semicircular path of radius r and are again combined into one pipe and superposed as shown in the figure. If the velocity of sound waves in the pipe is v, then frequencies of resultant waves of maximum amplitude will be integral multiples of

    WBJEE 2014

    (A) v/ [r(π - 2)]

    (B) v/ [r(π - 1)]

    (C) 2v/ [r(π - 1)]

    (D) v/ [r(π + 1)]

    Ans: (A)


    WBJEE 2014

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