KVPY Government Jobs Exams

A speaker emits a sound wave of frequency f0. When it moves towards a stationary observer with speed u,
the observer measures a frequency f1. If the speaker is stationary, and the observer moves towards it with
speed u, the measured frequency is f2. Then -
(A) f1 = f2 < f0 (B) f1 > f2 (C) f1 < f2 (D) f1 = f2 > f0

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KVPY Other Question
Jet aircrafts fly at altitudes above 30,000 ft where the air is very cold at – 40ºC and the pressure is 0.28 atm.
The cabin is maintained at 1 atm pressure by means of a compressor which exchanges air from outside
adiabatically. In order to have a comfortable cabin temperature of 25ºC, we will require in addition -
(A) a heater to warm the air injected into the cabin
(B) an air-conditioner to cool the air injected into the cabin
(C) neither a heater nor an air-conditioner ; the compressor is sufficient
(D) alternatively heating and cooling in the two halves of the compressor cycle A plane polarized light passed through successive polarizers which are rotated by 30º with respect to each
other in the clockwise direction. Neglecting absorption by the polarizers and given that the first polarizer's
axis is parallel to the plane of polarization of the incident light, the intensity of light at the exit of the fifth
polarizer is closest to -
(A) same as that of the incident light (B) 17.5% of the incident light
(C) 30% of the incident light (D) zero