Page-12

Physical Science

161)Television signal cannot be received ordinarily beyond a particular distance due to
weakness of the signal weak antenna
curvature of the earth absorption of signals in the air
Answer :

162)What is the use of a radar?
for receiving signals in a radio receiver for studying the movement of planets
detecting the position of aeroplanse for studying sunspots
Answer :

163)If you stand in a room, where two adjecent walls are covered with plane mirrors then total number of your images will be
2 infinite
3 5
Answer :

164)Assertion : The acceleration due to gravity increases with height above the earth's surface
Reason : Gravitational force increases with height
Both Assertion and Reason are correct and Reason explains Assertion Both Assertion and Reason are correct and Reason does not explain Assertion
Assertion is correct but Reason is wrong Both Assertion and Reason are wrong
Answer :

165)Assertion : Objects appear weightless inside an orbiting spacecraft.
Reason : Objects in circular motion experience centripetal force
Both Assertion and Reason are correct and Reason explains Assertion Both Assertion and Reason are correct and Reason does not explain Assertion
Assertion is correct but Reason is wrong Both Assertion and Reason are wrong
Answer :

166)Assertion : The earth revolves around the sun in ellliptical orbit
Reason: The sun always attracts the earth with the same force.
Both Assertion and Reason are correct and Reason explains Assertion Both Assertion and Reason are correct and Reason does not explain Assertion
Assertion is correct but Reason is wrong Both Assertion and Reason are wrong
Answer :

167)Assertion : A steel needle can be made to float on water
Reason: When an object is immersed in water it experiences an upthrust.
Both Assertion and Reason are correct and Reason explains Assertion Both Assertion and Reason are correct and Reason does not explain Assertion
Assertion is correct but Reason is wrong Both Assertion and the Reason are wrong
Answer :


168)Assertion : Apool of water looks ahallower than it actually is
Reason : Light bends towards the normal while travelling from water to air.
Both Assertion and Reason are correct and Reason explains Assertion Both Assertion and Reason are correct and Reason does not explain Assertion
Assertion is correct but Reason is wrong Both Assertion and Reason are wrong
Answer :

169)What type of mirror is used in the head lamps of a car?
Plane mirror Spherical concave mirror
Spherical convex mirror parabolic concave mirror
Answer :

170)The sun remain visible for some time after it actually sets below the horizon, due to
scattering of light atmospheric refraction of light
dispersion of light persistence of vision
Answer :

171)If there were no atomosphere, the length of the day would
increase decrease
remian unchanged be half