IIT-JEE Exam

The focal length of a thin biconvex lens is 20 cm. When an object is moved from a distance of 25 cm in
front of it to 50 cm, the magnification of its image changes from m25 to m50. The ratio m1/m2 is

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IIT-JEE Other Question

A binary star consists of two starts A (mass 2.2. MS) and B (mass 1 MS), where MS is the mass of the sun.
They are separated by distance d and are rotating about their center of mass, which is stationary. The ratio
of the total angular momentum of the binary star to the angular momentum of star B about the center of
mass is. A 0.1 kg mass is suspended form a wire of negligible mass. The length of the wire is 1 m and its cross–
sectional area is 4.9 × 10–7 m2. If the mass is pulled a little in the vertically downward direction and
released, it performs simple harmonic motion of angular frequency 140 rad s–1. If the Young's modulus of
the material of the wire is n × 109 Nm–2, the value of n is