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# Physics MCQ Questions  with Answer for all Competitive Exams

## Physics MCQ Questions  with Answer

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Q76. A ‘black hole’ is a body in space that does not allow any radiation to come out. This property is due to its:

(a) Very small size

(b) Very large size

(c) Very high density

(d) Very low size

 Answer: (c)Explanation:  A black hole is a region of space from which nothing not even light, can escape. It is the result of the deformation of space-time caused by a very compact mass. The simplest black hole has mass but neither electric charge nor angular momentum. The mass of a black hole is finite, the reason why a black hole has infinite density is that its mass is concentrated into a space of zero volume. Thus, it has a very high density.

Q77. When a ray of light enters a glass slab, then

​(a) ​Only the frequency changes ​

(b)​ Frequency and velocity change ​

(c)​ Frequency does not change ​

(d) ​Frequency and wavelength change

 Answer: (c)​Explanation: As the light enters from a rarer medium to the denser medium the speed of light decreases but the frequency remains the same.

Q78. Match List I with List-II and select the correct answer using the code given below the Lists:​​

 List-I (Physical quantity) List-II (Unit) A. Distance 1. Mole B. Amount of material 2. Coulomb C. Amount of electrical charge 3. Light year D. energy 4. Watt-hour

Code: A B C D

(a)        3 1 2 4

(b)       3 2 1 4

(c)        4 2 1 3

(d)       4 1 2 3

 Answer: ​(a)​Explanation: Large distance is measured in a light year. The amount of material is measured by a mole. The amount of electrical charge is measured in the coulomb. Energy is measured in watt-hour.

Q79. The ozone layer above the surface of Earth provides a shield against

(a) X-rays

(b) Ultra Violet Rays

(c) Gamma Rays

(d) Infrared Rays

 Answer: (b)Explanation: The ozone layer consists of O3 molecules, it protects the earth’s atmosphere from harmful ultra-violet rays.

Q80. Which of the following is not a part of a CRT?

(a) Phosphor Screen

(c) Electron Gun

(d) Gas Plasma

 Answer: (d)Explanation: In a cathode ray tube images are produced when an electron beam strikes a phosphor-coated screen. Its basic components are an electron gun, deflecting coils, phosphor-coated screen, shadow mask, etc.

Q81.​  ​ The displacement (x)-time (t) graph given above approximately represents the motion of a ​

(a)​ Simple pendulum placed in a vacuum ​

(b) Simple pendulum immersed in water ​

(c) ​Simple pendulum placed in outer space

​(d) ​Point mass moving in the air

 Answer: (b)Explanation: ​When a simple pendulum is immersed in water then its oscillations are damped and its wave is a cosine wave.

Q82. An oil tanker is partially filled with oil and moves forward on a level road with uniform acceleration. The free surface of oil then ​

(a)​ remains horizontal. ​

(b) ​is inclined to the horizontal with smaller depth at the rear end. ​

(c) ​is inclined to the horizontal with a larger depth at the rear end. ​

(d)​ Assumes parabolic curves.

 Answer: ​(c)​Explanation: The two points in the same horizontal line do not have equal pressure if the liquid is accelerated horizontally. The free surface of the oil is inclined to the horizontal with a larger depth at the rear end as the oil tanker is moving forward with uniform acceleration.

Q83. ​Consider the following statements: ​

​1. Light of a longer wavelength is scattered much more than the light of a shorter wavelength.

​2.​ The speed of visible light in water is 0.95 times the speed in a vacuum. ​

3.​ Radio waves are produced by rapidly oscillating electrical currents. ​

4.​ To detect the overspeeding of vehicles, police use the Doppler Effect to reflected short radio waves. ​

Which of these statements are correct? ​

(a) ​1 and 2

​(b)​ 1 and 3 ​

(c) ​2 and 4 ​

(d)​ 3 and 4

 Answer: ​(d)​Explanation: Radio waves are produced by rapidly oscillating electrical currents. For detecting over speeding of vehicles, police use the Doppler Effect to reflected short radio waves. The scattering of light is inversely proportional to its wavelength so, the longer the wavelength, the less it is scattered, the speed of visible light in matter is almost 3/4th the speed of light in a vacuum.

Q84. Light travels fastest in

(a) Nitrogen

(b) Air

(c) Steel

(d) Vacuum

 Answer: (d)Explanation: Light travels in a vacuum with a speed of 3×10 8 m/s.

Q85. The spokes used in the wheel of a bicycle increase its

(a) Moment of inertia

(b) Velocity

(c) Acceleration

(d) Momentum

 Answer: (a)Explanation: The spokes used in the wheel of a bicycle increase its moment of inertia. The more is the moment of inertia, the smoother will be the motion of the bicycle

Q86. Assertion (A): A piece of copper and a piece of glass are heated to the same temperature. When touched, thereafter, the copper piece appears hotter than the glass piece.

Reason (R): The density of copper is more than that orgies

Codes:

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not a correct explanation of A

(c) A is true but R is false

(d) A is false but R is true

 Answer: (b)Explanation: Both statement 1 and statement 2 are correct. On heating up to the same temperature copper piece is found hotter than in comparison to glass piece because copper being a metal is a good conductor of heat and electricity while the glass, on the other hand, is a poor conductor of heat. The density of copper is 8.92 gm/ cm3 and of glass is 2.6 gm/cm.

Q87. Consider the following statements: ​

1.​ A flute of smaller length produces waves of lower frequency. ​

2.​ Sound travels in rocks in the form of longitudinal elastic waves only. ​

Which of the statement(s) given above is/are correct? ​

(a)​ 1 only ​

(b)​ 2 only

​(c)​ Both 1 and 2 ​

(d) Neither 1 nor 2

 Answer: ​(b)​ Explanation: As frequency ∝ 1/length, so flute will produce waves of higher frequency. Sound waves are transmitted through gas, plasma, and liquid as longitudinal waves but through solids, they can be transmitted both longitudinal as well as transverse waves.

Q88. The function of ball bearings in a wheel is:

(a) To increase friction

(b) To convert kinetic friction into rolling friction

(c) To convert static friction into kinetic friction

(d) Just for convenience

 Answer: (b)Explanation: The main function of ball bearings is to reduce friction between the surface of the bearing and the surface it is rolling over.

Q89. Action and reaction _____.

(a) Always act on the same body

(b) Are equal in magnitude

(c) Are in the same direction

(d) Always act independently

 Answer: (b)Explanation: Newton’s Third Law of Motion states that for every action there is an equal and opposite reaction. Action and reaction forces are always equal in magnitude but opposite in direction.

Q90. Which mirror is used as a rearview mirror in the vehicles? ​

(a)​ Plane

​(b)​ Convex ​

(c)​ Concave

​(d) ​Inverted

 Answer: (b)​Explanation: Convex mirror is used as a rearview mirror in Motor vehicles.

Q91. The Law of Inertia is also known as _____.

(a) Newton’s first law of motion

(b) Newton’s second law of motion

(c) Newton’s third law of motion

(d) None of these

 Answer: (a)Explanation: Law of Inertia is also known as Newton’s First Law of Motion. Newton’s First Law of Motion states that an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless an external force is applied to it.

Q92. What happens to a liquid, when the vapour pressure equals the atmospheric pressure?

(a) The liquid cools

(b) The liquid boils

(c) No change

(d) The liquid evaporates

 Answer: (b)Explanation: The condition when the vapour pressure of the liquid is equal to the atmospheric pressure is termed as Boiling. Hence at that temperature, the liquid boils.

Q93. Assertion (A): The boiling point of water decreases as the altitude increases.

Reason (R): The atmospheric pressure increases with altitude.

Codes: (a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but it is not a correct explanation of A

(c) A is true but R is false

(d) A is false but R is true

 Answer: (c)Explanation: The boiling point of an element or a substance is the temperature at which the vapour pressure of the liquid equals the environmental pressure surrounding the liquid. As altitude increases atmospheric pressure decreases, so the boiling point decreases, so the liquid would boil at a lower temperature.

Q94. Ultrasonics is sound waves of frequency ​

(a)​ Greater than 20,000 Hz ​

(b) ​Less than 10,000 Hz ​

(c)​ Equal to 1000 Hz

​(d) ​None of these

 Answer: ​(a)​Explanation: Ultrasonic is defined as acoustic frequencies greater than 16-20 kHz up to 1 GHz and is not audible to the human ear.

Q95. Which of the following is not scalar quantity? ​

(a)​ Time ​

(b)​ Volume ​

(c)​ Density ​

(d) ​Momentum

 Answer: ​(d)​Explanation: Momentum is a vector quantity. A vector quantity possesses both a magnitude and a direction.

Q96. An image formed by a concave mirror on a screen is called __________?

(a) Virtual image

(b) Real image

(c) Inverted image

(d) Erect image

 Answer: (b)Explanation: Concave mirror forms a real and inverted image of an object.

Q97. A hollow sphere of radius R, a hollow cube of side 12, and a thin circular plate of radius R, made up of the fame material, are all heated to 20°C above room temperature. When left to cool in the room, which of them will reach the room temperature first?

(a) Circular plate

(b) Cube

(c) Sphere

(d) All of them, will reach room temperature at the same time

 Answer: (c)Explanation: The loss of heat is directly proportional to the surface area, hence loss of hoot will be earlier in the case of sphere because it has the maximum surface area.

Q98. Which electromagnetic radiation is used for satellite communication?

(a) Ultraviolet

(b) Infrared

(c) Microwave

(d) Millimeter-wave

 Answer: (c)Explanation: Microwaves have short wavelengths and high frequency, hence they pass through the earth’s atmosphere and can reach satellites easily.

Q99. Cloudy nights are warmer compared to clear cloudless nights because clouds:

(a) Prevent clod waves from the sky from descending on earth

(b) Reflect back the heat given off by the earth

(c) Produce heat and radiate it towards the earth

(d) Absorb heat from the atmosphere and send it towards the earth

 Answer: (b)Explanation: Cloudy nights are warmer than clear nights because the cloud cover provides a shield that acts as an insulator and stores up the heat radiated by the earth and do not permit heat to escape.

Q100. When we hear a sound, we can identify its source from

(a) Wavelength of sound

(b) The overtones present in the sound

(c) The intensity of sound

(d) The amplitude of the sound

 Answer: (b)Explanation: The overtones present in the sound give us knowledge of the source as every source has a fixed fundamental frequency. When instruments are played above fundamental frequency overtones can be recognized.

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