# Physics Questions and Answers – Part9

81. Sound produced at a point is heard by a person after 5 second, while the same sound is heard by another person after 6 seconds. If the speed of sound is 300 m/s, what could be the maximum and minimum distances between the two persons?
a. 1.8 km, 0.15 km
b. 2.2 km, 0.20 km
c. 2.8 km, 0.25 km
d. 3.3 km, 0.30 km
d. 3.3 km, 0.30 km

82. Intensity of sound at a point is ____ its distance from the source.
a. directly proportional to
b. inversely proportional to
c. directly proportional to square of
d. inversely proportional to square of
d. inversely proportional to square of

83. Of the four locations mentioned below the highest inside temperature will be attained in the pressure cooker operated with the pressure valve open
a. at sea level
b. at the top of Mt. Everest
c. at a place in a valley below sea level
d. in an aeroplane flying at a height of 10,000 m with inside pressure maintained at the sea level
c. at a place in a valley below sea level

84. Radio telescopes are better than optical telescopes because
a. they can detect faint galaxies which no optical telescope can
b. they can work even in cloudy conditions
c. they can work during the day and night
d. All of the above
d. All of the above

85. Light Emitting Diodes (LED) is used in fancy electronic devices such as toys emit
a. X-rays
b. ultraviolet light
c. visible light
c. visible light

86. Out of the following pairs, which one does not have identical dimension?
a. Moment of inertia and moment of a force
b. Work and Torque
c. Angular momentum and Planck’s constant
d. Impulse and Momentum
a. Moment of inertia and moment of a force

87. Mercury is commonly used as a thermometric fluid rather than water because
a. specific heat of mercury is less than water
b. specific heat of mercury is more than water
c. mercury has greater visibility than water
d. density of mercury is more than the water
c. mercury has greater visibility than water

88. Optical fibre works on the
a. principle of refraction
b. total internal reflection
c. scattering
d. interference
b. total internal reflection

89. Light from the star, Alpha Centauri, which is nearest to the earth after the sun, reaches the earth in
a. 4.2 seconds
b. 42 seconds
c. 4.2 years
d. 42 years