Physics Questions and Answers Part-16

1. Sound following a flash of lightning is called
a) Stoning
b) Bolting
c) Thunder
d) Cloud clash

Answer: c
Explanation: Sound following a flash of lightning is called Thunder. Thunder or thunder clap always follows lightning because light travels faster than sound. Thunder is caused by the rush of air into the space, created by lightning as it travels from cloud to earth.

2. Acceptable noise level for human ear
a) 85 db
b) = 85 db
c) < 85 db
d) None of the above

Answer: c
Explanation: Because people can't hear all frequencies, or pitches of sound, A-weighted decibels (dBA) can be used to describe sound based on what human ears can actually hear. Sounds at or below 70 dBA are generally considered safe. Any sound at or above 85 dBA is more likely to damage your hearing over time.

3. Decibel is a term connected with :
a) air
b) water
c) sound
d) soil

Answer: c
Explanation: Decibel is a term connected with sound.

4. Decibel is the unit used for
a) Speed of light
b) Intensity of heat
c) Intensity of sound
d) Radio wave frequency

Answer: c
Explanation: Decibel is the unit used for intensity of sound.

5.The speed of sound in air depends on
a) Frequency
b) temperature
c) Wavelength
d) None of the Above

Answer: b
Explanation: The speed of sound in air depends on the type of gas and the temperature of the gas. On Earth, the atmosphere is composed of mostly diatomic nitrogen and oxygen, and the temperature depends on the altitude in a rather complex way.

6. Fish and other aquatic creatures can live inside a deep frozen pond because
a)Fish are cold-blooded animals
b) Ice is a bad conductor of heat
c) There will always be water just beneath the ice level
d) They can adapt themselves to live in ice

Answer: c
Explanation: All liquids have a boiling point and a freezing point. Underneath the frozen upper layer, the water remains in its liquid form and does not freeze. Also, oxygen is trapped beneath the layer of ice. As a result, fish and other aquatic animals find it possible to live comfortably in the frozen lakes and ponds.

7. The density of a gas is maximum at
a) Low temperature, low pressure
b) Low temperature, high pressure
c) High temperature, low pressure
d) High temperature, high pressure

Answer: b
Explanation: The density of gases depends upon the temperature. The higher the temperature, the more the molecules are spread out and the lower the density.

8. Lakes freeze in cold countries in winter, leaving the water underneath at
a) 0°C
b) 0°F
c) 4°C
d) 4°F

Answer: c
Explanation: Freezing takes place at he top of the lake this is because water colder than 4 degree celsius usually starts to expand and get less dense as it gets colder. It is the liquid with more density that settles at the bottom while the less denser floats above it.

9. A bimetal made copper and iron strips welded together is straight at room temperature. It is held vertically with iron strip towards left and copper strip towards right. If this bimetal is heated, it will
a) Remain straight
b) Bend towards right
c) Bend towards left
d) None of these

Answer: c
Explanation: Since the strips are welded together, the combined strip will bend towards left ( towards iron ) since copper strip will have more length than the iron strip.

10. Thermal expansion of materials arises from
a) Strong bonds
b) Thermal vibrations
c) Weak bonds
d) Asymmetry of potential energy curve

Answer: d
Explanation: Thermal expansion of materials arises from asymmetry of potential energy curve.