Physics

101. Which one of the following is NOT a luminous object ?

Which one of the following is NOT a luminous object ?

[amp_mcq option1=”Sun” option2=”Electric lamp” option3=”Candle” option4=”Moon” correct=”option4″]

This question was previously asked in
UPSC CAPF – 2019
Download PDFAttempt Online
The correct answer is D) Moon.
Objects can be classified based on whether they produce their own light or merely reflect light from another source.

* **Luminous Objects:** These objects emit their own light.
* A) Sun: The Sun is a star that produces light and heat through nuclear fusion. It is a luminous object.
* B) Electric lamp: An electric lamp (like an incandescent bulb, fluorescent tube, or LED lamp) produces light when electricity is passed through it. It is a luminous object.
* C) Candle: A burning candle produces light through the process of combustion. It is a luminous object.
* **Non-luminous Objects:** These objects do not produce their own light but become visible because they reflect light from a luminous source.
* D) Moon: The Moon does not generate its own light. We see the Moon because it reflects sunlight. Therefore, the Moon is a non-luminous object.

Most objects we see around us on Earth, such as furniture, books, trees, etc., are non-luminous. They are visible because they reflect ambient light from sources like the Sun or artificial lamps.

102. Brilliance of diamond is due to

Brilliance of diamond is due to

[amp_mcq option1=”interference of light” option2=”diffraction of light” option3=”polarization of light” option4=”total internal reflection of light” correct=”option4″]

This question was previously asked in
UPSC CAPF – 2019
Download PDFAttempt Online
The extraordinary brilliance and sparkle of a cut diamond are primarily due to its high refractive index and the specific angles at which its facets are cut, which together facilitate total internal reflection of light within the stone. Light entering the diamond undergoes multiple reflections before exiting, creating the sparkling effect.
– Total Internal Reflection (TIR) occurs when light travels from a denser medium to a less dense medium at an angle greater than the critical angle.
– Diamond has a very high refractive index (around 2.42), resulting in a small critical angle (around 24.4 degrees).
– The precise cutting of diamond facets is designed to maximise TIR, ensuring that a large amount of light is reflected back out through the top of the stone, enhancing its brilliance (white light reflection) and fire (dispersion of light into spectral colours).

103. Which one of the following is NOT an electromagnetic wave ?

Which one of the following is NOT an electromagnetic wave ?

[amp_mcq option1=”Light wave” option2=”Radio wave” option3=”Sound wave” option4=”Micro wave” correct=”option3″]

This question was previously asked in
UPSC CAPF – 2019
Download PDFAttempt Online
Sound waves are mechanical waves that require a medium (like air, water, or solids) to propagate. They are typically longitudinal waves in fluids.
– Electromagnetic waves are disturbances that can travel through a vacuum (like space) as well as through matter. They consist of oscillating electric and magnetic fields.
– Light waves, radio waves, and microwaves are all examples of electromagnetic waves, differing in their frequency and wavelength.
– The electromagnetic spectrum includes, in order of increasing frequency/energy and decreasing wavelength: Radio waves, Microwaves, Infrared radiation, Visible light, Ultraviolet radiation, X-rays, and Gamma rays.
– Sound waves are caused by vibrations that create pressure variations in the medium.

104. Which one of the following is NOT true for an electromagnetic wave ?

Which one of the following is NOT true for an electromagnetic wave ?

[amp_mcq option1=”Electromagnetic wave transports energy and momentum” option2=”Electromagnetic wave can be polarized and reflected” option3=”Electromagnetic wave is longitudinal” option4=”Electromagnetic wave propagation is described by the varying electric and magnetic fields” correct=”option3″]

This question was previously asked in
UPSC CAPF – 2019
Download PDFAttempt Online
Electromagnetic waves are transverse waves, not longitudinal. In a transverse wave, the oscillations of the wave are perpendicular to the direction of wave propagation.
– Electromagnetic waves consist of oscillating electric and magnetic fields that are perpendicular to each other and to the direction of propagation.
– They transport both energy and momentum.
– Being transverse waves, they can be polarized. They also undergo reflection, refraction, diffraction, and interference.
– Longitudinal waves, such as sound waves in air, involve oscillations parallel to the direction of propagation.
– The statement that electromagnetic wave propagation is described by varying electric and magnetic fields is fundamental to Maxwell’s equations, which govern their behaviour.

105. A snowboard pulled up by a tow rope travels at the rate of 5 m/s up a

A snowboard pulled up by a tow rope travels at the rate of 5 m/s up a mountain. If 3000 watt of power is used, what force was applied to it ?

[amp_mcq option1=”50 N” option2=”100 N” option3=”600 N” option4=”15000 N” correct=”option3″]

This question was previously asked in
UPSC CAPF – 2019
Download PDFAttempt Online
The relationship between power (P), force (F), and velocity (v) when the force is applied in the direction of motion is given by the formula P = F * v.
– Given Power (P) = 3000 watts.
– Given velocity (v) = 5 m/s.
– We need to find the force (F).
– Rearranging the formula, F = P / v.
– Substituting the given values, F = 3000 W / 5 m/s = 600 N.
– Therefore, the force applied to the snowboard was 600 Newtons.

106. The number of neutrons inside the nucleus of the element Uranium-235

The number of neutrons inside the nucleus of the element Uranium-235 is

[amp_mcq option1=”235″ option2=”92″ option3=”143″ option4=”51″ correct=”option3″]

This question was previously asked in
UPSC CAPF – 2019
Download PDFAttempt Online
The number 235 in Uranium-235 is the mass number (A), which is the total number of protons and neutrons in the nucleus. Uranium (U) has an atomic number (Z) of 92, meaning it has 92 protons. The number of neutrons (N) is calculated by subtracting the atomic number from the mass number: N = A – Z.
– Mass number (A) = Number of protons + Number of neutrons.
– Atomic number (Z) = Number of protons.
– For Uranium-235, A = 235 and Z = 92.
– Number of neutrons = 235 – 92 = 143.
– Uranium has several isotopes, including Uranium-238 (most common, 146 neutrons) and Uranium-235 (used in nuclear reactors and weapons, 143 neutrons).

107. When a longitudinal wave moves through a certain medium, the quantity

When a longitudinal wave moves through a certain medium, the quantity which is transmitted through the medium is

[amp_mcq option1=”material of the medium only” option2=”energy only” option3=”both material of the medium and energy” option4=”none of the above” correct=”option2″]

This question was previously asked in
UPSC CAPF – 2019
Download PDFAttempt Online
When a longitudinal wave moves through a medium, it is the energy that is transmitted through the medium, not the material itself. The particles of the medium oscillate about their equilibrium positions but do not travel long distances with the wave.
– A wave is a disturbance that transfers energy from one point to another.
– In a longitudinal wave, particles of the medium vibrate parallel to the direction of wave propagation.
– Examples of longitudinal waves include sound waves in air and pressure waves in fluids.
– This principle applies to both longitudinal and transverse mechanical waves; the medium oscillates but does not propagate. Electromagnetic waves also transmit energy and momentum through space without needing a physical medium, relying on oscillating fields.

108. Which of the following are the most favourable conditions for liquefyi

Which of the following are the most favourable conditions for liquefying a gas ?

[amp_mcq option1=”Low pressure and high temperature” option2=”Low pressure and low temperature” option3=”High pressure and high temperature” option4=”High pressure and low temperature” correct=”option4″]

This question was previously asked in
UPSC CAPF – 2019
Download PDFAttempt Online
Liquefying a gas requires bringing its molecules closer together and reducing their kinetic energy so that intermolecular attractive forces become dominant. This is best achieved by applying high pressure (to reduce the space between molecules) and lowering the temperature (to reduce molecular motion).
– High pressure forces gas molecules closer, increasing the likelihood of intermolecular attractions.
– Low temperature reduces the kinetic energy of molecules, allowing attractive forces to overcome disruptive thermal motion.
– Every gas has a critical temperature above which it cannot be liquefied by pressure alone, regardless of how high the pressure is. Liquefaction is only possible at or below the critical temperature.
Below the critical temperature, the substance is called a vapor, and it can be liquefied by applying sufficient pressure. Above the critical temperature, it remains a gas even under high pressure; increasing pressure only increases its density, forming a supercritical fluid above the critical pressure. Therefore, high pressure and low temperature relative to the critical point are the most favorable conditions.

109. Directions : The following eight (8) items consist of two statements,

Directions :
The following eight (8) items consist of two statements, Statement I and Statement II. Examine these two statements carefully and select the correct answer using the code given below.
Code :
Statement I : A compass needle placed near a current-carrying wire will get deflected.
Statement II : A current-carrying wire creates magnetic field around it.

[amp_mcq option1=”Both the statements are individually true and Statement II is the correct explanation of Statement I” option2=”Both the statements are individually true but Statement II is not the correct explanation of Statement I” option3=”Statement I is true but Statement II is false” option4=”Statement I is false but Statement II is true” correct=”option1″]

This question was previously asked in
UPSC CAPF – 2018
Download PDFAttempt Online
The correct answer is A) Both the statements are individually true and Statement II is the correct explanation of Statement I.
– Statement I: A compass needle is a small magnet. It aligns itself with the local magnetic field. If a compass needle is placed near a current-carrying wire, it will experience a force due to the magnetic field produced by the current, causing it to deflect. This statement is true.
– Statement II: A current-carrying wire produces a magnetic field around it. This phenomenon was discovered by Hans Christian Ørsted and is a fundamental principle of electromagnetism, described by laws like Ampère’s law. This statement is true.
– Statement II provides the reason why the compass needle in Statement I gets deflected. The magnetic field created by the current-carrying wire (Statement II) is what causes the deflection of the compass needle (Statement I).
The direction and strength of the magnetic field around a straight current-carrying wire can be determined using the right-hand rule and the Biot-Savart Law or Ampère’s Law. The deflection of the compass needle demonstrates the presence and direction of this magnetic field.

110. Directions : The following eight (8) items consist of two statements,

Directions :
The following eight (8) items consist of two statements, Statement I and Statement II. Examine these two statements carefully and select the correct answer using the code given below.
Code :
Statement I : Sound waves can travel through vacuum.
Statement II : Light is an electromagnetic wave and can travel through vacuum.

[amp_mcq option1=”Both the statements are individually true and Statement II is the correct explanation of Statement I” option2=”Both the statements are individually true but Statement II is not the correct explanation of Statement I” option3=”Statement I is true but Statement II is false” option4=”Statement I is false but Statement II is true” correct=”option4″]

This question was previously asked in
UPSC CAPF – 2018
Download PDFAttempt Online
The correct answer is D) Statement I is false but Statement II is true.
– Statement I: Sound waves are mechanical waves. They require a medium (solid, liquid, or gas) for propagation because they travel through the vibration of particles in the medium. Vacuum is devoid of such particles, hence sound cannot travel through vacuum. This statement is false.
– Statement II: Light waves are electromagnetic waves. Electromagnetic waves do not require a material medium for propagation; they can travel through vacuum. This is why light from the Sun reaches the Earth through the vacuum of space. This statement is true.
Electromagnetic waves travel at the speed of light ($c$) in vacuum. Sound waves travel at much slower speeds, which depend on the properties of the medium.
Page 1Page 2Page 3Page 4Page 5