IIT JEE Physics Final Revision Set 15

Two waves y1 = A cos( 0.5 πx − 100 πt)
and y2 = A cos( 0.46 πx − 92 πt) are travelling in a pipe placed along x-axis.

1. Find the number of times
intensity is maximum in time interval of 1 sec.
(A) 4 (B) 6
(C) 8 (D) 10


2. Find wave velocity of louder sound
(A) 100 m/s (B) 192 m/s
(C) 200 m/s (D) 96 m/s

3. Find the number of times y1+ y2 = 0 at x = 0 in 1 sec
(A) 100 (B) 46
(C) 192 (D) 96

4.In an insulated vessel, 0.05 kg steam at 373 K and 0.45 kg of ice at 253 K are mixed. Then, find the final
temperature of the mixture.
Given, L(fusion) = 80 cal/g = 336 J/g, L(vaporization) = 540 cal/g = 2268 J/g,
S(ice) = 2100 J/kg K = 0.5 cal/gK and S(water) = 4200 J/kg K = 1 cal /gK

5. In hydrogen-like atom (z = 11), "n"th line of Lyman series has wavelength λ equal to the de-Broglie’s wavelength of electron in the level from which it originated. What is the value of n?

Source: JEE 2006