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

The correct answer is scattering of light

Key Points

• When the sun is near the horizon during the morning or evening, it appears reddish. The phenomenon that is responsible for this observation is the scattering of light.
• The sunlight comprises 7 colors Violet, Indigo, Blue, Green, Yellow, Orange, and Red out of these Violet has the lowest wavelength and red has the highest.
• In the morning and the sunset, the sunlight has to travel more distance through the atmosphere of the earth to reach us.
• So, only the colours having high wavelengths reach us, and colours with low wavelengths get miss in midway because of scattering by air, moisture, smoke, and other dust particles in the atmosphere.
• The astronaut will not observe this phenomenon on the moon’s surface, because the moon has no atmosphere. Therefore no light will be distributed, and darkness will arise

Additional Information Reflection

• It 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.

Refraction

• In physics, refraction is the change in the direction of a wave passing from one medium to another or from a gradual change in the medium.
• Refraction of light is the most commonly observed phenomenon, but other waves such as sound waves and water waves also experience refraction.

Dispersion

• In optics, dispersion is the phenomenon in which the phase velocity of a wave depends on its frequency.
• Media having this common property may be termed dispersive media. Sometimes the term chromatic dispersion is used for specificity.

The correct answer is Just before it touches the ground.

Key Points

• When an object reaches the ground it has its maximum value of kinetic energy just before touching the ground.
  • Since kinetic energy + potential energy = Constant, so on reaching the ground, the potential energy of an object becomes zero. 
  • So eventually, the kinetic energy on reaching the ground becomes maximum.

Additional Information

• Kinetic energy is the work needed to accelerate a body of a given mass from rest to its stated velocity.
  • K.E. =  mv², where, m= mass of the body, v= velocity of the given group. 
• Potential energy is stored energy that depends upon the relative position of various system parts.
  • P.E. = mg h, where, m= mass of the body, g= gravitational acceleration, h= height.
• When the stone was at top of the roof it has P.E. = maximum, K.E.= zero. Because the stone was in idle condition so velocity, v=0, K.E.=0.
  • Just after the stone is dropped, P.E. is started reducing, and the velocity is increasing, which in turn increases its K.E.
  • When the stone is just halfway, K.E. and P.E. just become half of their actual values.
  • When the stone touches the ground, its velocity v=0, so K.E. =0, and P.E. again get restored to its original value.
• The law of conservation of energy states that energy can neither be created nor destroyed, it transforms from one form to another.
  • So in the course of the stone dropped from the roof of a house to its reaches at the ground, K.E. and P.E. transform between each other.
  • But every time, K.E. + P.E. = Total energy = Constant must be maintained.   

The correct answer is Changing the shape of the body.

Key Points

• The rate of change of displacement is called velocity.
• Velocity is a vector quantity, which has both magnitude and direction.
• SI Unit of velocity is m/sec.
• It may be positive or negative.
• If a body is moving on a circular then after completing one complete cycle, its average velocity is zero.
• The velocity of an object is the speed of an object moving in a definite direction.
• Velocity changes with the speed and direction of motion of the body.
• Changing the shape of the body will not affect the velocity of the body.

The correct answer is 2) 1 and 2 only.

Key Points

• Flattening of the Sun's disc at sunrise and sunset (Statement 1) occurs due to atmospheric refraction, which bends sunlight as it passes through denser layers of the atmosphere near the horizon.
• Reddening of the Sun at sunrise and sunset (Statement 2) is caused by scattering of shorter wavelengths (blue and violet) of sunlight, leaving predominantly red light visible.
• Atmospheric refraction refers to the bending of light rays due to the varying density of Earth's atmosphere.
• Formation of a rainbow (Statement 3) is primarily due to dispersion, refraction, and internal reflection of light in water droplets, not atmospheric refraction.
• Thus, Statements 1 and 2 are correct, and the phenomenon described in Statement 3 is unrelated to atmospheric refraction.

Additional Information

• Atmospheric Refraction: This phenomenon occurs when light passes through layers of the atmosphere with varying densities, leading to bending of light rays. It is responsible for various optical phenomena like the apparent position of stars and the flattening of the Sun near the horizon.
• Scattering of Light: The process by which small particles and molecules in the atmosphere scatter shorter wavelengths of sunlight (blue and violet) more effectively than longer wavelengths (red). This causes the sky to appear blue during the day and the Sun to appear red at sunrise and sunset.
• Dispersion: The separation of white light into its constituent colors when it passes through a medium (e.g., a prism or water droplets). This is the primary cause of rainbow formation.
• Rainbow Formation: A rainbow is formed when sunlight undergoes refraction, internal reflection, and dispersion inside water droplets in the atmosphere. It appears in a direction opposite to that of the Sun.
• Horizon Effects: Near the horizon, sunlight travels through a greater thickness of the atmosphere, leading to enhanced scattering and refraction effects, which contribute to phenomena like the Sun's flattening and reddening.

The correct answer is 0 N.

Key Points

• When a body is moving with uniform velocity, there is no acceleration acting on the body.
• According to Newton's Second Law of Motion, the net force on an object is directly proportional to its acceleration (F = ma).
• If the acceleration is zero (as in uniform velocity), the net force acting on the object is 0 N.
• This is consistent with the concept of equilibrium, where forces acting on the body are balanced, resulting in constant velocity.
• Uniform velocity implies the absence of unbalanced external forces, hence the net force remains zero.

Additional Information

• Newton's First Law of Motion (Law of Inertia):
  • A body at rest or in uniform motion will remain in that state unless acted upon by an external force.
  • This explains why the net force is zero when velocity is uniform.
• Newton's Second Law of Motion:
  • The law states that the force (F) on an object is equal to the mass (m) of the object multiplied by its acceleration (a), expressed as F = ma.
  • Zero acceleration leads to zero net force.
• Uniform Velocity:
  • It refers to motion at a constant speed in a straight line.
  • Neither the magnitude nor the direction of velocity changes.
• Equilibrium in Physics:
  • When all forces acting on a body are balanced, the body is in a state of equilibrium.
  • In such cases, the net force is zero, and the body either remains at rest or moves with uniform velocity.

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 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 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

Distance travelled = 2d = v × t

⇒ 2 × d = 342 × 2

⇒ d = (342 × 2)/2

⇒ d = 342 m

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 = 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

From the Lens equation,

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

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  .
  • Where 'f' - frequency of the source, 'L' - Inductance, and 'C' - Capacitance.

Additional Information 

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.