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 0^{th} layer enters the 1^{st} layer at an angle of incidence of 30°. After undergoing the m^{th} refraction, the ray emerges parallel to the interface. If μ = 1.5 and Δμ = 0.015, the value of m is

(A) 20

(B) 30

(C) 40

(D) 50

**Ans: (D)**

**Sol:**

By using Snell’s law:

**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)**

** **

**Sol:**

**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 ω_{1} : ω_{2} : ω_{3} is

(A) 1 : 1: 1

(B) √2 : √2 : 1

(C) 1 : √2 : 1

(D) 1 : 2 : √2

**Ans: (B)**

** **

**Sol:**

We know that,

**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 *w*_{1} and *w*_{2} respectively. If the densities of the two constituent metals are *ρ _{1} *and

*ρ*respectively, then the weight of the first metal in the sample is (where

_{2}*ρ*is the density of water)

_{w}**Ans: (A)**

** **

**Sol:**

**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

(A) v/ [r(π - 2)]

(B) v/ [r(π - 1)]

(C) 2v/ [r(π - 1)]

(D) v/ [r(π + 1)]

**Ans: (A)**

** **

**Sol:**

**Also Get:**

**WBJEE Previous Years' Question Papers**