Top 30 Physics MCQs for Competitive Exams

பல்வேறு போட்டித் தேர்வுகளில் இயற்பியல் முக்கியப் பங்காற்றுகிறது, விண்ணப்பதாரர்களுக்கு அவர்களின் தயாரிப்பில் உதவ, நாங்கள் 30 கேள்விகளை (MCQs) தொகுத்துள்ளோம். உங்கள் இயற்பியல் அறிவை மேம்படுத்துவதற்கும், வரவிருக்கும் தேர்வுகளுக்கு உங்களை சிறப்பாக தயார்படுத்துவதற்கும் ஒவ்வொரு கேள்விக்கும் சரியான பதில் உள்ளது.

Top 30 Physics MCQs

Q1.Which of the following is the correct definition of sound?

(a) The transmission of light waves

(b) The transmission of electromagnetic waves

(d) The transmission of radio waves

Q2.Sound waves are characterized by which of the following properties?

(a) Amplitude and frequency

(b) Wavelength and speed

(d) Diffraction and interference

Q3.The unit of measurement for frequency is:

(a) Decibel

(b) Hertz

(d) Pascal

Q4.Which of the following materials would generally transmit sound the best?

(a) Vacuum

(b) Water

(d) Rubber

Q5.What is the term for the bending of sound waves as they pass through different mediums with varying densities?

(a) Diffraction

(b) Reflection

(d) Refraction

Q6.The speed of sound is highest in which of the following gases?

(a) Oxygen

(b) Carbon dioxide

(d) Nitrogen

Q7.Which part of the human ear is responsible for amplifying sound vibrations?

(a) Cochlea

(b) Eardrum (tympanic membrane)

(d) Auditory nerve

Q8.What is the term for a sound wave that combines multiple frequencies?

(a) Pitch

(b) Harmonic

(d) Noise

Q9.The phenomenon of interference in sound waves occurs when:

(a) Sound waves reflect off a surface

(b) Sound waves bend around obstacles

(d) Sound waves change direction when passing through a medium

Q10.Which of the following devices converts sound waves into electrical signals?

(a) Microphone

(b) Speaker

(d) Amplifier

Q11. An air bubble in water will act like a:

(a) Convex mirror

(b) Convex lens

(d) Concave lens

Q12. When we see an object, the image formed on the retina is ________

(a) Real and inverted

(b) Real and erect

(d) Virtual and inverted

Q13. Which one of the following processes is responsible for the glittering of air bubbles rising through water?

(a) Reflection of light

(b) Refraction of light

(d) Scattering of light

Q14. What is the phenomenon which established the transverse nature of light?

(a) Reflection

(b) Interference

(d) Polarization

Q15. The remove the defect of long-sightedness one uses-

(a) Concave lens

(b) Convex mirror

(d) Concave mirror

Q16. The angle between the __________ and the incident ray is called the angle of incidence.

(a) Surface

(b) Normal

(d) Reflected ray

Q17. An image formed by a concave mirror on a screen is called __________

(a) Virtual image

(b) Real image

(d) Erect image

Q18.When an object is placed at infinity, the image formed by a converging lens is:

(a) Real, inverted, and magnified

(b) Virtual, upright, and magnified

(d) Virtual, upright, and reduced

Q19.When an object is placed between the focal point and the lens of a diverging lens, the image formed is:

(a) Real, inverted, and magnified

(b) Virtual, upright, and magnified

(d) Virtual, upright, and reduced

Q20.Which type of lens is commonly used in magnifying glasses?

(a) Convex lens

(b) Concave lens

(d) Plano-concave lens

Q21. Why it is easier to swim in the sea than in a river?

(a) The sea water is salty

(b) The sea water is deep

(d) The sea water is lighter

Q22. Light from the Sun reaches Earth in about:

(a) 2 minutes

(b) 4 minutes

(d) 16 minutes

Q23. Which one of the following is used as a moderator in the nuclear reactor?

(a) Thorium

(b) Graphite

(d) Ordinary water

Q24. Which of the following is not used as rocket propellant?

(a) Liquid hydrogen

(b) Liquid oxygen

(d) Kerosene oil

Q25. Spherical form of raindrop is due to-

(a) Density of liquid

(b) Surface tension

(d) Gravitational force

Q26. The half-life of a radioactive substance is 10 day; it means there will be:

(a) complete decay of substance in 20 days

(b) complete decay of substance of 40 days

(d) decay of ¼ part of substance in 5 days

Q27. In the night wind blows fast, dew is not formed because

(a) Rate of evaporation is fast

(b) Moisture in air is low

(d) Sky is not clear

Q28. CT Scan is done by using-

(a) Infra-red Rays

(b) Ultrasonic Waves

(d) X-Rays

Q29. Which device is used to measure the depth of ocean?

(a) Lexometer

(b) Nanometer

(d) Hydrometer

Q30. GPS stands for which one of the following?

(a) Greenwich Polar Satellite

(b) Global Police Surveillance

(d) General Pacific Survey

Solution:

S1.Ans(c)

Sol.The transmission of mechanical waves through a medium. Sound is a form of mechanical wave that travels through a medium, such as air, water, or solids. It requires a medium for its propagation.

S2.Ans(a)

Sol. Amplitude refers to the maximum displacement of particles in the medium from their rest position, while frequency represents the number of oscillations or cycles of the wave per second.

S3.Ans(b)

Sol. Frequency is measured in hertz (Hz), which represents the number of cycles or vibrations per second.

S4.Ans(b)

Sol. Sound waves travel more efficiently through denser mediums, and water is denser than air. Therefore, water is a better conductor of sound than the other options.

S5.Ans(d)

Sol. Refraction occurs when sound waves change direction as they pass from one medium to another due to the variation in the speed of sound in different materials.

S6.Ans(c)

Sol. Helium has a lower molecular weight compared to other gases, resulting in faster sound propagation. Hence, the speed of sound is highest in helium.

S7.Ans(c)

Sol. The ossicles, consisting of the malleus, incus, and stapes, amplify sound vibrations from the eardrum and transmit them to the inner ear.

S8.Ans(d)

Sol. Noise refers to a mixture of sound waves with different frequencies and amplitudes,

S9.Ans(c)

Sol. Interference in sound waves occurs when two or more sound waves meet at a point and interact with each other. Depending on their relative phases, interference can result in constructive or destructive interference, altering the overall amplitude of the combined wave.

S10.Ans(a)

Sol. A microphone is a device that converts sound waves into electrical signals. It contains a diaphragm that vibrates in response to sound waves, which, in turn, generates corresponding electrical signals that can be amplified and processed for various applications.

S11. Ans.(d)

Sol.

When light passes from a denser medium (water) to a rarer medium (air), it undergoes refraction. The refractive index of water is higher than that of air. As light enters the air bubble in water, it bends away from the normal, which is the line perpendicular to the surface of the water.
Due to this refraction, the light rays converge after passing through the air bubble. When these converging rays are extended backward, they appear to originate from a point in front of the air bubble, creating a virtual image. This behavior is similar to how a concave lens forms an image. Therefore, an air bubble in water behaves like a concave lens,

S12. Ans.(a)

Sol. When we see an object, the image formed on the retina is real and inverted.

The image formed on the retina of our eye is produced through the process of refraction. Light from an object enters the eye, passes through the lens, and converges onto the retina, which is a light-sensitive layer located at the back of the eye. The lens of the eye helps focus the incoming light onto the retina.
In this process, the image formed on the retina is real, meaning it is formed at the actual location where the light converges. The image is also inverted, meaning it appears upside down compared to the actual object.

Therefore, option (a) real and inverted is the correct choice.

S13. Ans.(c)

Sol.

The glittering or sparkling of air bubbles rising through water is primarily caused by (c) total internal reflection of light.
Total internal reflection occurs when light traveling from a denser medium (water) to a less dense medium (air) reaches the boundary between the two at an angle greater than the critical angle. In the case of air bubbles rising through water, light rays entering the bubble from the water undergo multiple internal reflections within the bubble’s curved surface due to the change in refractive index.
These internal reflections cause the light to scatter in various directions, resulting in the sparkling or glittering effect observed. The phenomenon is similar to how light is reflected within a prism or a diamond, creating a display of colors and reflections.

Therefore, option (c) total internal reflection of light is the process responsible for the glittering of air bubbles rising through water.

S14. Ans.(d)

Sol. The phenomenon that established the transverse nature of light is polarization.

Polarization refers to the orientation of the electric field vector associated with a light wave. It was observed and studied extensively by French physicist Augustin-Jean Fresnel in the early 19th century. Through his experiments and analysis, Fresnel established that light consists of transverse waves, meaning the oscillations of the electric and magnetic fields are perpendicular to the direction of propagation.
When light is polarized, its electric field oscillates in a specific direction, and the wave vibrations occur in a plane perpendicular to that direction. This phenomenon was crucial in understanding the wave nature of light and differentiating it from other types of waves.

Therefore, option (d) polarization is the phenomenon that established the transverse nature of light.

S15. Ans.(c)

Sol. To correct the defect of long-sightedness, one uses a convex lens.

Long-sightedness, also known as hypermetropia or farsightedness, is a condition where a person has difficulty seeing nearby objects clearly. In long-sightedness, the focal point of the eye’s lens falls behind the retina instead of directly on it.
To correct long-sightedness, a convex lens is used. A convex lens is thicker at the center and thinner at the edges, and it converges light rays to a focal point. By using a convex lens, the light entering the eye is refracted in such a way that it converges on the retina, allowing for clear vision of nearby objects.

Therefore, option (c) convex lens is the correct choice for correcting the defect of long-sightedness.

S16.Ans.(b)

Sol. The angle between the (b) normal and the incident ray is called the angle of incidence.

The normal is a line perpendicular to the surface at the point where the incident ray strikes it. The incident ray is the incoming ray of light that strikes a surface. The angle of incidence is defined as the angle between the incident ray and the normal.
When light strikes a surface, the angle of incidence plays a crucial role in determining how the light will be reflected or refracted at that surface. It helps determine the direction and behavior of the light as it interacts with the surface.

Therefore, option (b) normal is the correct term for the line involved, and the angle between the normal and the incident ray is called the angle of incidence.

S17.Ans.(b)

Sol. An image formed by a concave mirror on a screen is called a real image.

A concave mirror is a curved mirror with its reflecting surface curved inward. When an object is placed in front of a concave mirror beyond its focal point, the mirror reflects and converges the incoming light rays. This convergence of light rays forms an image.
In the case of a concave mirror, if the object is placed at a distance greater than the focal length, a real image is formed on a screen or surface. A real image is formed when the reflected light rays actually converge and intersect at a specific point, resulting in a focused image that can be projected onto a screen or captured on a surface.

Therefore, option (b) real image is the correct description for the image formed by a concave mirror on a screen.

S18.Ans(d)

Sol.When an object is placed at infinity, a converging lens forms a virtual, upright, and reduced image.

S19.Ans(b)

Sol. When an object is placed between the focal point and the lens of a diverging lens, a virtual, upright, and magnified image is formed.

S20.Ans(a)

Sol.The type of lens commonly used in magnifying glasses is (a) convex lens.

A convex lens is thicker at the center and thinner at the edges. It is also known as a converging lens because it causes parallel light rays to converge or come together after passing through it. The convex shape of the lens allows it to bend light inward and focus it.
When a convex lens is used in a magnifying glass, it creates a magnified virtual image of an object placed within its focal length. This virtual image is larger and appears to be located behind the lens. By bringing the magnifying glass close to the object and looking through it, the viewer can observe a magnified and enlarged view of the object.

Therefore, option (a) convex lens is the correct choice for the type of lens commonly used in magnifying glasses.

S21. Ans.(a)

Sol. It is easier to swim in sea water than in a river because, the sea water contains salt which increases the density of water and also increases its upthrust so, the chances of sinking get reduced and one can easily swim in such water.

S22. Ans.(c)

Sol. The correct answer is (c) 8 minutes.

Light from the Sun takes approximately 8 minutes to reach Earth. This value is often rounded to 8 minutes and 20 seconds for simplicity. The exact time it takes for light to travel from the Sun to Earth can vary slightly due to the elliptical shape of Earth’s orbit and the varying distance between the two bodies throughout the year. However, on average, it takes about 8 minutes for sunlight to reach our planet.

S23. Ans.(b)

Sol.The correct answer is (b) Graphite.

Graphite is commonly used as a moderator in nuclear reactors. A moderator is a material that slows down fast-moving neutrons produced during nuclear fission reactions. By slowing down the neutrons, the probability of their interaction with other fissile atoms, such as uranium-235 or plutonium-239, increases. This facilitates the sustained chain reaction necessary for the efficient operation of a nuclear reactor.

Graphite is an excellent moderator because it contains carbon atoms, which have a relatively low atomic mass and can effectively slow down neutrons. Other materials, such as heavy water (which contains the isotope deuterium) or ordinary water (when used in conjunction with enriched uranium fuel), can also act as moderators, but graphite is a more common choice in many types of reactors.

S24. Ans.(d)

Sol.

The correct answer is (d) Kerosene oil.

Kerosene oil is not typically used as a rocket propellant. It is commonly used as a fuel in various other applications, such as heating, lamps, and jet engines, but it is not commonly used as a propellant in rockets.

On the other hand, the other options listed—liquid hydrogen, liquid oxygen, and hydrazine—are commonly used as rocket propellants:

Liquid hydrogen: Liquid hydrogen is used as a rocket propellant in combination with liquid oxygen (LOX) in some rocket engines. The combination of liquid hydrogen and liquid oxygen produces a high specific impulse, making it an efficient propellant for certain types of rockets, such as those used in the space shuttle.
Liquid oxygen: Liquid oxygen is frequently used as an oxidizer in rocket engines. It reacts with a fuel source, such as liquid hydrogen or kerosene, to produce combustion and generate thrust.
Hydrazine: Hydrazine is a commonly used rocket propellant and is often used as a monopropellant or a component in bipropellant systems. It is a highly energetic and toxic compound, making it suitable for rocket propulsion.

S25. Ans.(b)

Sol.

The correct answer is (b) Surface tension.

The spherical form of a raindrop is primarily due to surface tension. Surface tension is a phenomenon that occurs at the interface between two different substances, such as a liquid and a gas. In the case of raindrops, the surface tension of water molecules at the air-water interface causes the liquid to adopt a spherical shape.

Surface tension is the result of cohesive forces between the water molecules, which tend to minimize the surface area of the liquid. In the absence of external forces, a raindrop will naturally assume a spherical shape, as this shape minimizes the surface area for a given volume. This is because a sphere has the smallest surface area-to-volume ratio among all shapes.

S26. Ans. (c)

Sol. The half life of a radioactive substance is 10 days; it means in next 10 days there will be half of the remaining radioactive substance. Thus, total 20 days, there will be decay of 75% or ¾ part of substance.

S27. Ans.(a)

Sol. Dew is not formed on the night of strong wind as due to strong wind the rate of evaporation is fast. Thus, the particles of the dew tend to evaporate.

S28. Ans.(d)

Sol. CT scan, also known as computed tomography, is a medical imaging technique that uses X-rays to create detailed cross-sectional images of the body. It involves taking a series of X-ray images from different angles around the body, and then a computer processes these images to produce a three-dimensional representation of the internal structures. X-rays are a form of electromagnetic radiation with higher energy than visible light, and they can penetrate through the body to varying degrees, allowing the detection of different tissues and structures.

S29. Ans.(c)

Sol. The device used to measure the depth of the ocean is called a fathometer. Therefore, the correct option is (c) Fathometer.

Nanometer: A nanometer is a unit of length in the metric system, equal to one billionth of a meter. It is used to measure very small distances, typically on the scale of atoms and molecules.
Hydrometer: A hydrometer is an instrument used to measure the density or specific gravity of a liquid. It is commonly used in various fields, including chemistry and brewing.

S30. Ans.(c)

Sol.

GPS stands for Global Positioning System. It is a satellite-based navigation system that provides location and timing information anywhere on Earth. The system consists of a network of satellites orbiting the Earth, ground-based control stations, and GPS receivers. GPS receivers receive signals from multiple satellites and use the timing and location information embedded in those signals to calculate the receiver’s precise location. GPS technology is widely used for navigation, mapping, surveying, and various other applications.

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