Physics MCQ Quiz - Objective Question with Answer for Physics - Download Free PDF

The correct answer is Statement I and III are correct.

Key Points

• Statement I: The frequency of vibration determines the pitch of the sound. This statement is correct as the pitch is directly related to the frequency of the sound wave; higher frequency results in higher pitch.
• Statement II: A higher frequency of vibration produces a lower pitch. This statement is incorrect as higher frequency corresponds to a higher pitch.
• Statement III: Amplitude affects the loudness of the sound. This statement is correct as the loudness of a sound is determined by its amplitude; higher amplitude results in louder sound.

Additional Information

• Pitch: The perceived frequency of a sound; it is how high or low a sound seems to a listener.
• Frequency: The number of vibrations or cycles per second of a sound wave, measured in Hertz (Hz).
• Amplitude: The height of the sound wave, which determines the loudness or volume of the sound.
• Loudness: A subjective perception of sound pressure, influenced by the amplitude of the sound wave.
• Sound waves are characterized by their wavelength, frequency, amplitude, and speed, which together determine the sound's pitch, loudness, and quality.

The correct answer is Ironing clothes.

Key Points

• Conduction is the process of heat transfer through direct contact between materials.
• When ironing clothes, heat is transferred from the hot iron to the fabric through direct contact, exemplifying conduction.
• This process relies on the thermal conductivity of the materials involved, such as the metal surface of the iron and the fabric of the clothes.
• Conduction is most effective in solids where particles are closely packed and can transfer energy efficiently by vibrating against each other.

Additional Information

• Convection
  • Convection is the transfer of heat through the movement of fluids (liquids or gases).
  • Examples include boiling water where heat is transferred through the movement of water molecules.
  • It occurs because of the fluid's tendency to expand and rise when heated, creating a convection current.
• Radiation
  • Radiation is the transfer of heat through electromagnetic waves without involving particles.
  • The Sun heating the Earth is a prime example of radiation.
  • It does not require a medium and can occur in a vacuum.
• Thermal Conductivity
  • Thermal conductivity is a property of a material that indicates its ability to conduct heat.
  • Metals have high thermal conductivity, making them effective conductors of heat.
  • Materials with low thermal conductivity, like wood and plastic, are used as insulators.
• Heat Transfer
  • Heat transfer is the process of heat energy moving from a hotter object to a cooler one.
  • It can occur through conduction, convection, or radiation.
  • Understanding heat transfer is crucial in various applications, from industrial processes to everyday activities like cooking and heating homes.

The correct answer is Option 1: Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion..

Key Points

• Metal pans are used for cooking because they are excellent conductors of heat, allowing heat to distribute evenly across the cooking surface.
• The high thermal conductivity of metals like aluminum, copper, and stainless steel helps in efficient cooking by transferring heat quickly from the stove to the food.
• Using metal pans ensures that food is cooked uniformly, preventing hotspots and reducing cooking times.
• The reason provided aligns with the assertion as it explains how the good heat-conducting property of metal pans facilitates quick and efficient cooking.

Additional Information

• Thermal Conductivity: The measure of a material's ability to conduct heat. Metals like copper and aluminum have high thermal conductivity, making them ideal for cooking utensils.
• Heat Distribution: Even heat distribution is crucial in cooking to ensure that food cooks uniformly without burning or undercooking in certain spots.
• Stainless Steel: Often used in cookware, it combines durability and resistance to rust, although it is less conductive than copper or aluminum.
• Heat Transfer Mechanism: Heat transfer in cooking occurs through conduction, convection, and radiation, with conduction being the primary method in metal pans.

The correct answer is option 1.

Key Points

• The Sun's light reaches Earth through reflection.
• The Moon's light is reflected sunlight.
• The Moon does not generate its own light; it reflects the Sun's light that falls on its surface.
• The process of reflection involves the bouncing back of light rays when they hit a surface.
• Both the Sun's and Moon's light reaching Earth is due to the phenomenon of reflection.

Additional Information

• Reflection:
  • Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated.
  • Common examples include the reflection of light, sound, and water waves.
  • Mirrors exhibit specular reflection, meaning they reflect light in a single direction, maintaining the image's clarity.
• Refraction:
  • Refraction is the bending of light as it passes from one medium to another with different densities.
  • It occurs due to the change in the speed of light in different media.
  • Examples include light bending when passing through water or a glass lens.
• Absorption:
  • Absorption is the process by which matter takes up photons of light and converts the energy into internal energy.
  • Materials that absorb light may appear dark or opaque.
  • Absorption plays a significant role in phenomena like the greenhouse effect.
• The Moon's Surface:
  • The Moon's surface is covered with fine dust and rocky debris, which reflects sunlight.
  • The reflectivity of the Moon is relatively low, with an albedo of about 0.12, meaning it reflects only 12% of the sunlight that hits it.
  • This reflection is what makes the Moon visible from Earth.

The correct answer is Sun.

Key Points

• The Sun is a massive ball of hot gases that emits light and heat energy, making it a primary source of light for our solar system.
• It is classified as a G-type main-sequence star (G dwarf) based on its spectral class.
• The Sun generates energy through nuclear fusion, primarily converting hydrogen into helium in its core.
• As a luminous object, the Sun’s energy output is approximately 3.8 x 10^26 watts, which sustains life on Earth and drives various ecological processes.

Additional Information

• Luminous Objects
  • These are objects that generate and emit their own light, such as stars, light bulbs, and fireflies.
  • Luminous objects are crucial for visibility and energy transfer in various ecosystems.
• Non-Luminous Objects
  • These objects do not produce their own light but can reflect light from luminous sources, such as the Moon, planets, and most solid objects on Earth.
  • They are visible due to the reflection or scattering of light from luminous objects.
• Photosphere
  • The photosphere is the visible surface layer of the Sun that emits the light we see.
  • It has an average temperature of about 5,500 degrees Celsius (5,773 Kelvin).
• Nuclear Fusion
  • Nuclear fusion is the process that powers the Sun, where hydrogen nuclei combine to form helium, releasing enormous amounts of energy.
  • This process occurs in the Sun’s core under extreme temperatures and pressures.

CONCEPT:

• Wave: The disturbance that transfers energy from one place to another is called a wave.

There are mainly two types of waves:

1. Transverse waves: The wave in which the movement of the particles is at right angles to the motion of the energy is called a transverse wave. Light is an example of a transverse wave.
2. Longitudinal wave: The wave in which the movement of the particles is parallel to the motion of the energy is called a longitudinal wave. The sound wave is an example of a longitudinal wave.

EXPLANATION:

• Light-wave is a transverse wave because its components vibrate perpendicular to its direction of propagation. So option 1 is correct.

The correct answer is Newton's first law.

Key Points

• Newton's laws of motion-
  • ​Newton’s first law states that, if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by force.
    • This postulate is known as the law of inertia. The law of inertia was first formulated by Galileo Galilei for horizontal motion on Earth and was later generalized by René Descartes.
    • Before Galileo, it had been thought that all horizontal motion required a direct cause. Still, Galileo deduced from his experiments that a body in motion would remain in motion unless a force (such as friction) caused it to come to rest.
  • Newton’s second law is a quantitative description of the changes that a force can produce in a body's motion.
    • It states that the time rate of change of a body's momentum is equal in both magnitude and direction to the force imposed on it.
    • The momentum of a body is equal to the product of its mass and its velocity. Momentum, like velocity, is a vector quantity, having both magnitude and direction.
    • A force applied to a body can change the magnitude of the momentum, direction, or both.
    • For a body whose mass m is constant, it can be written in F = ma, where F (force) and an (acceleration) are vector quantities.
    • If a body has a net force acting on it, it is accelerated by the equation. Conversely, if a body is not accelerated, there is no net force acting on it.
  • Newton’s third law states that when two bodies interact, they apply forces to one another that are equal in magnitude and opposite in direction.
  • The third law is also known as the law of action and reaction. This law is important in analyzing static equilibrium problems, where all forces are balanced, but it also applies to bodies in uniform or accelerated motion.
  • The forces it describes are real ones, not mere bookkeeping devices. For example, a book resting on a table applies a downward force equal to its weight on the table.
  • According to the third law, the table applies an equal and opposite force to the book. This force occurs because the book's weight causes the table to deform slightly so that it pushes back on the book like a coiled spring.

The correct answer is At the centre of the Earth.

• The centre of the Earth is such that if we are at that place, the mass around us can be considered to be condensed at the surface of the Earth itself, i.e considering the Earth as a spherical shell.
• Inside a spherical shell, there is no change in potential as one moves inside, and since only a change in potential implies a force there is no force.
• Hence the acceleration due to gravity is zero at the centre of the Earth.

The correct answer is 342 m.

CONCEPT:

• Echo: If we shout or clap near a suitable reflecting object such as a tall building or a mountain, we will hear the same sound again a little later. This sound which we hear is called an echo.
  • Echoes are heard due to the phenomenon of Reflection of sound waves.
  • To hear the echo clearly, the reflecting object must be more than 17.2 m from the sound source for the echo to be heard by a person standing at the source.

CALCULATION:

Speed of sound = 342 m/s.

The time is taken for hearing an echo = 2s.​

• The speed of sound is

\(⇒ Speed (v)= \frac{distance (d)}{time (t)}\)

Distance travelled = 2d = v × t

⇒ 2 × d = 342 × 2

⇒ d = (342 × 2)/2

The correct answer is Gamma Rays.

Key Points

• Gamma rays have the shortest wavelength and highest frequency (energy) in the electromagnetic spectrum.
• They are electromagnetic waves with wavelengths in the range of 10^-12m and frequencies around 10²⁰- 10²⁴ Hz.
• They have a high penetrating power.
• They are a result of decaying radioactive material and can also be found in outer space.
• They are used in medical applications for sterilisation of equipment and cancer treatment.

Additional Information

•  Other radiations in the Electromagnetic spectrum are:

The correct answer is the Microwave.

Key Points

• A microwave oven uses microwaves to heat food.
• In the case of microwave ovens, the commonly used radio wave frequency is roughly 2,500 megahertz (2.5 gigahertz).
• Radio waves in this frequency range absorbed by water, fats, and sugars. When they are absorbed they are converted directly into atomic motion or vibration.
• Therefore heavy motion or vibration is converted into heat.

Important Points

• Microwaves are not absorbed by most plastics, glass, or ceramics.
• The frequency of the Microwave equals the resonance frequency of water. Therefore foods could be heated up by the oscillation of water molecules.

Additional Information

• An Electric heater, Electric blub (with filament), Electric iron is the electrical device that converts an electric current into heat.
• They working on the principle of the Joule heating effect.
  • An electric current passing through a resistor will convert that electrical energy into heat energy.

The correct answer is 12250 W.

Concept:

• Power: Power is the amount of energy transferred or converted per unit time.
  • The unit of power is watt or J/s.
  • Its dimensional formula is: [M L² T^-3].

Calculation:

Given: v = 700 m/s, m = 50 g = 0.05 kg, n/t = 60 bullets/min ⇒  1 bullet/s

The power developed by the gun is given by formula -

Power = Work done / time = Energy consumed / time

\(Power = n \times \frac{{\frac{1}{2}m{v^2}}}{t}\)

\(Power = \frac{n}{t}\; \times \frac{1}{2}m{v^2}\)

\(Power = 1 \times \frac{1}{2} \times 0.05 \times {700^2}\)

Power = 12250 watt

Calculations:

Given,

Distance of the object from the lens = u = -10 cm

Refractive index of the lens = µ = 1.5

The Radii of curvature of the lens are 20 cm in magnitude

R₁ = 20 cm and R₂ = -20 cm          (As per sign convention)

According to Len's Maker's formula

\(\frac{1}{f}=(\mu - 1)(\frac{1}{R_1}-\frac{1}{R_2})=(1.5-1)(\frac{1}{20}-\frac{1}{-20})\\ =0.5 \times \frac{2}{20}=\frac{1}{20}\\ or, \; f=20 \; cm \)

From the Lens equation,

\(\frac{1}{v}-\frac{1}{u}=\frac{1}{f}\\ \frac{1}{v}=\frac{1}{f}+\frac{1}{u}\\ or, \; v=\frac{fu}{u+f}=\frac{20 \times (-10)}{-10+20}=\frac{-200}{10}=-20 \; cm\)

The image is formed 20 cm on the same side as the object.

The correct answer is 10-4 microns.

Key Points

Read the question ,it is asking value  in microns not meter.

If asked in meters then the value will be 1 Angstroms  = 10^-10 m.

But asked in microns

• 1 mm = 10^-3 m
• 1 micron = 10^-3 mm
  • ⇒ 1 micron = 10-6 m
• 1 Angstrom = 10^-10 m
  • 1 Angstrom = 10-10 m = 10-10 × 106 micron = 10-4 micron.

Confusion Points

1 Angstrom = 10^-10 meter

1 Angstrom =  10^-4 micron

Additional Information

• An Angstrom is a unit of length used to measure very small distances.
• 1 Angstroms to = 0.0001 Microns 
• It is named after Anders Jonas Ångström (Swedish physicist).
• A micron is one-millionth of a meter (10−6 m) and one Angstrom is 10-4 micron.

The correct answer is Ohm.

Key Points

• Impedance is the total sum of resistance and reactance.
• The SI Unit of Impedance(Z), resistance(R), and reactance(X) is Ohm(Ω).
• Reactance is a kind of imaginary resistance offered by electrical components like Capacitance and Inductor.
  • Reactance offered by the Inductor is called Inductive reactance, given as X_L = 2πfL.
  • Reactance offered by the Capacitor is called Capacitor reactance, given as  \(X_{C}=\frac{1}{2\pi fC}\).
  • Where 'f' - frequency of the source, 'L' - Inductance, and 'C' - Capacitance.

Additional Information