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

The correct answer is Meter per second (m/s).

Key Points

• The SI unit for speed is meter per second (m/s), which is the standard unit used in scientific measurements.
• Although speed limits on highways are commonly displayed in kilometers per hour (km/h) or miles per hour (mph) for practical reasons, the fundamental SI unit remains m/s.
• Speed is a measure of the distance traveled per unit of time, and the use of m/s is consistent with the metric system used globally.
• In everyday usage, different countries may prefer km/h or mph depending on regional standards, but m/s is universally accepted for scientific contexts.

Additional Information

• Speed in Different Units:
  • 1 m/s = 3.6 km/h
  • 1 m/s ≈ 2.237 mph

Correct Answer: 3 and 5 only. Key Points

• Air - 1.0003
  The refractive index of air is correctly matched. The typical value for air is around 1.0003.

• Benzene - 1.50
  The refractive index of benzene is correctly matched. The refractive index for benzene is around 1.50.

• Diamond - 2.42
  The refractive index of diamond is incorrectly matched. The correct refractive index of diamond is approximately 2.42, not 1.77.

• Water - 1.33
  The refractive index of water is correctly matched. The refractive index of water is 1.33.

• Turpentine oil - 1.47
  The refractive index of Turpentine oil is not correctly matched. It is 1.47, not 1.07.

The correct answer is 1) Plane mirror.

Key Points

• Plane mirrors are the most commonly used mirrors for personal grooming, such as face viewing and makeup application.
• They provide a clear, upright, and undistorted reflection of objects placed in front of them.
• Plane mirrors produce images that are of the same size as the object and maintain the same proportions.
• The image formed by a plane mirror is virtual (not real) and appears to be located behind the mirror at the same distance as the object in front.
• Plane mirrors are used in homes, bathrooms, dressing rooms, and even in optical instruments for basic reflection purposes.

Additional Information

• Concave Mirror:
  • Concave mirrors are curved inward and are used to focus light, often in telescopes, headlights, and shaving mirrors.
  • They can form both real and virtual images, depending on the object's distance from the mirror.
  • When used for face viewing, they magnify the image, making them useful for detailed tasks like shaving.
• Convex Mirror:
  • Convex mirrors are curved outward and are primarily used for wide-angle views, like in vehicle side mirrors.
  • They always produce virtual, upright, and diminished images, making them unsuitable for face viewing.
• Virtual Image:
  • A virtual image is formed when the reflected rays appear to meet behind the mirror.
  • Plane mirrors and convex mirrors always form virtual images.
• Reflection of Light:
  • The phenomenon of light bouncing back from a surface is called reflection.
  • The angle of incidence is always equal to the angle of reflection, as per the law of reflection.

The correct answer is Specific Gravity.

• Centre of gravity is an imaginary point in a body of matter where the entire weight of an object acts.
• This is sometimes useful in designing static structures (e.g., buildings and bridges) or tp predict the behaviour of a moving body when it is acted on by gravity.

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.