1210+ Physics Solved MCQs

1201.

The velocity of sound in moist air is more than in dry air because the moist air has

A. less density than city air
B. less pressure than dry air
C. more pressure than dry air
D. more density than dry air
Answer» A. less density than city air
Explanation: The density of dry air is more than that of moist air (when moisture is removed from air, its density. increases). The speed of sound in a medium is inversely proportional to the square root of its density. Therefore, the speed of sound in moist air is more than that in dry air.
1202.

The owl can see most clearly in total darkness because –

A. it has squint eyes
B. it has large eyes with orbs directed forward, giving it binocular sight
C. it has light bulbs in its eyes provided by nature
D. it produces infrasonic sounds
Answer» B. it has large eyes with orbs directed forward, giving it binocular sight
Explanation: Because of their eyes, an owl can see much better in the dark than we can. Owls have very large eyes which maximize light gathering in conditions of minimum light, thereby enabling them to see at night. The orbs of their eyes are directed forward, giving them binocular vision. They are able to see their prey in a three-dimensional manner. However, an owl's eye cannot rotate.
1203.

Water boils at a lower temperature on the hills because –

A. it is cold on the hills
B. there is less carbon dioxide on the hills
C. there is a decrease in air pressure on the hills
D. There is less oxygen
Answer» C. there is a decrease in air pressure on the hills
Explanation: Water boils at a lower temperature on top of a mountain because there is less air pressure on the molecules. Water boils when the vapor pressure of water exceeds atmospheric pressure. Because the boiling temperature is lower at high elevations foods that are cooked by boiling take a little longer to cook at high elevation.
1204.

Bats can sense obstacles because they produce –

A. supersonic sound waves
B. ultrasonic sound waves
C. infrasonic sound waves
D. micro sound waves
Answer» B. ultrasonic sound waves
Explanation: The reason that bats use ultrasound is because it has such a high frequency and it has a low diffraction or it bends less. They use this sound to do a couple of things like to catch their prey and also just to get around. The method of doing such tasks is called echolocation. They make a sound and wait for it to bounce back to hear it. If they hear it come faster in a particular area than the rest of the sounds then they know that something is near.
1205.

A satellite in vacuum -

A. is kept in orbit by remote control
B. is kept in orbit by retro-rocket
C. derives energy from gravitational fielod
D. does not require any energy for orbiting
Answer» D. does not require any energy for orbiting
1206.

The sky appears blue because –

A. All colours interfere to produce blue
B. In white light, the blue component dominates
C. The atmosphere scatters blue colour more than the others
D. It is actually blue
Answer» C. The atmosphere scatters blue colour more than the others
Explanation: Diffuse sky radiation is solar radiation reaching the Earth's surface after having been scattered from the direct solar beam by molecules in the atmosphere. Of the total light removed from the direct solar beam by scattering in the atmosphere (approximately 25% of the incident radiation when the sun is high in the Sky.
1207.

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
Answer» C. mercury has greater visibility than water
Explanation: One special kind of mercury-in- glass thermometer, called a maximum thermometer, works by having a constriction in the neck close to the bulb.
1208.

A barometer is kept inside a bell jar. Air is slowly pumped out of the jar.

A. The mercury level starts rising
B. The mercury level starts falling
C. The mercury level does not change
D. The bell jar breaks up
Answer» A. The mercury level starts rising
Explanation: As the pump removes the air from the bell jar the pressure obviously reduces around the barometer. The reduction in pressure around the barometer leads it to expand. As the pump removes air from the jar, the mercury level rises.
1209.

Melting point of ice               .

A. increases with increase of pressure
B. decreases with increase of pressure
C. is independent of pressure
D. None of these
Answer» B. decreases with increase of pressure
Explanation: The melting point of ice at 1 atmosphere of pressure is very close to 0 °C (32
1210.

The threshold frequency is the frequency below which –

A. photo current increases with voltage
B. photo current decreases with voltage
C. photo electric emission is not possible
D. photo current is constant
Answer» C. photo electric emission is not possible
Explanation: The photoelectric effect is the emission of electrons by substances, especially metals, when light falls on their surfaces. The photoelectric effect will not occur when the frequency of the incident light is less than the threshold frequency as the electrons are unable to gain sufficient energy to overcome the electrostatic barrier of the work function of the metal.
1211.

The blue colour of sky is due to –

A. reflection of sunlight
B. refraction of sunlight
C. scattering of shorter wave-lengths of sunlight in the atmosphere
D. scattering of longer wave-lengths of sunlight in the atmosphere
Answer» C. scattering of shorter wave-lengths of sunlight in the atmosphere
Explanation: The blue colour of the sky is caused by the scattering of sunlight off the molecules of the atmosphere. This scattering, called Rayleigh scattering is more effective at short wavelengths (the blue end of the visible spectrum). Therefore the light scattered down to the earth at a large angle with respect to the direction of the sun's light is predominantly in the blue end of the spectrum.
1212.

Metal tea pots have wooden handles because –

A. wood is a bad conductor of heat
B. it prevents electric shock
C. it gives beauty to the pots
D. it is hygienic
Answer» B. it prevents electric shock
Explanation: Wood is a bad conductor of heat due to the arrangement of its molecules. As the molecules of wood are far from each other, they cannot pass heat through them.
1213.

Flywheel is an important part of a steam engine because it –

A. accelerates the speed of the engine
B. helps the engine in keeping the speed uniform
C. decreases the moment of inertia
D. gives strength to the engine
Answer» B. helps the engine in keeping the speed uniform
Explanation: A flywheel is a rotating mechanical device that is used to store rotational energy. Flywheels have a. significant moment of inertia and thus resist changes in rotational speed, enabling the engine to run at a constant, uniform motion. In the Industrial Revolution, James Watt contributed to the development of the flywheel in the steam engine.
1214.

The rice is cooked more quickly in a pressure cooker because –

A. it is covered.
B. less quantity of water is used.
C. None of these
D. water boils at a higher temperature under pressure.
Answer» D. water boils at a higher temperature under pressure.
Explanation: The rice can be cooked faster in a pressure cooker since the boiling point of water increases with pressure. In general, the higherthe temperature of the water, the faster the food will cook. The temperature of the water in a pressure cooker is higher than temperature of the water in an open pot.
1215.

Photophobia is -

A. a disease caused by too much sunlight
B. abnormal intolerance of light
C. the adjustment of the eye for light
D. the ability to perceive light
Answer» C. the adjustment of the eye for light
Explanation: Photophobia, or light sensitivity, is an intolerance of light. Sources such as sunlight, fluorescent light and incandescent light all can cause discomfort, along with a need to squint or close your eyes.
1216.

Where do the electrical charges reside in a charged conductor?

A. at the core
B. throughout the body
C. depended upon the nature of the body
D. outer surface of the body
Answer» D. outer surface of the body
Explanation: In all conductors, charges reside on the surface. The reason for this is that conductors have free electrons, that is, the electrons are loosely attached to the nucleus of the atoms in the conductors. When a solid conductor in equilibrium carries a net charge, the charge resides on the outer surface of the conductor. Besides, the electric field just, outside the conductor is perpendicular to the surface and that the field inside is zero.
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