17.A photodiode can detect a photon having a maximum wavelength of 2500A. The band gap for the photodiode is : (A) 2.45 eV (B) 3.16 eV (C) 5.52 eV (D) 4.96 eV 18.A package is dropped from the plane which is flying with a constant horizontal velocity at a height H from ground. How much time does it takes to cross the last 19% of its vertical fall? [g is acceleration due to gravity] 2H g 9 - (B) 10 2H g 2H (C) g (D) 2H 10 g 19.An -particle is constrained to move along y-axis with a speed of 0.01C [C is speed of light] in the presence of an electromagnetic wave, where electric field is E = 90(0.3 107t-10-2x)V/m. The maximum magnetic force experienced by the electron charge = 1.6 10-19 C) (A) 2.88 x 10-19 N (C) 2.88 x 10-20 N (B) 1.44 x 10-19 N (D) 1.44 x 10-20 N 20.A wheel P is rotating freely with an angular speed w on a shaft. The moment of inertia of the wheel P is I and the moment of inertia of the shaft is negligible. Another wheel Q of moment of inertia 31 initially at rest is suddenly coupled to the same shaft. The angular impulse of the frictional force imparted to the wheel P and the shaft system is : Iw 31w 31w Iw (A) + (B) + (C) - - (D) - 4 4