36. A pipe of length , closed at one end is kept in a chamber of gas of density . A second pipe open at both ends is placed in a second chamber of gas of density . The compressibility of both the gases is equal. Calculate the length of the second pipe if frequency of first overtone in both the cases is equal

a) b)

c) d)

Ans: b)

,

37. Three discs A, B and C having radii 2, 4, and 6 cm respectively are coated with carbon black. Wavelength for maximum intensity for the three discs are 300, 400 and 500 nm respectively. If , and are power emitted by A, B and C respectively, then

a) will be maximum

b) will be maximum

c) will be maximum

d)

Ans :b)

will be maximum.

38. Monochromatic light of wavelength 400 nm and 560nm are incident simultaneously and normally on double slits apparatus whose slits separation is 0.1 mm and screen distance is 1m. Distance between areas of total darkness will be

a) 4 mm b) 5.6 mm

c) 14 mm d) 28 mm

Ans: d)

by inspection, for

39. Shown in fig is a post office box. In order to calculate the value of external resistance, it should be connected between

a) B' and C' b) A and D

c) C and D d) B and D

Ans: b)

40. A disc is rolling without slipping with angular velocity . P and Q are two points equidistance from the centre C. The order of magnitude of velocity is

a) b)

c) d)

Ans: b)

About instantaneous axis of rotation i.e., point of contact , is maximum is maximum.