Physics

111. Which one of the following is anisotropic in nature?

Which one of the following is anisotropic in nature?

[amp_mcq option1=”Glass” option2=”Rubber” option3=”Plastic” option4=”Quartz” correct=”option4″]

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Quartz is a crystalline solid, and its physical properties (like refractive index, thermal conductivity, etc.) vary depending on the direction in which they are measured. This directional dependence of properties is known as anisotropy. Glasses, rubber, and most common plastics are amorphous solids (or largely amorphous), meaning their structure is disordered, and their properties are generally the same in all directions, making them isotropic.
Anisotropic materials have properties that vary with direction, typically due to their ordered internal structure (like crystals). Isotropic materials have properties that are the same in all directions, typically due to their disordered or randomly oriented structure (like amorphous solids or polycrystalline aggregates with randomly oriented grains).
Common examples of anisotropic materials include crystalline solids (like quartz, calcite, wood, and many metals in single crystal form). Isotropic materials include glass, amorphous polymers, liquids, and gases. Some materials can be made anisotropic through processing, like drawing plastic fibers or rolling metals, which introduces preferred orientation in the material’s structure.

112. Which one of the following processes is not a part of long-wave

Which one of the following processes is not a part of long-wave radiation?

[amp_mcq option1=”Conduction” option2=”Scattering” option3=”Convection” option4=”Radiation” correct=”option2″]

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Scattering is not typically considered a part of the processes fundamentally defining or transferring energy as long-wave radiation in the Earth’s energy budget, unlike Conduction, Convection, and Radiation (emission/absorption).
Long-wave radiation refers to thermal radiation emitted by the Earth’s surface and atmosphere, primarily in the infrared spectrum. The transfer of this thermal energy within the Earth system involves processes like:
– **Radiation:** Emission and absorption of long-wave electromagnetic waves.
– **Conduction:** Heat transfer through direct contact, significant at the Earth-atmosphere interface.
– **Convection:** Heat transfer through the movement of air or water, driven by temperature differences resulting from radiative heating/cooling.
Scattering is a process where radiation is deflected in different directions by particles or molecules. While radiation of all wavelengths can be scattered, scattering is a dominant process affecting the path of incoming *short-wave* solar radiation (e.g., causing the blue sky). It is not a primary mechanism for the *transfer* or *distribution* of the heat energy associated with outgoing *long-wave* radiation in the same way as conduction, convection, and emission/absorption of radiation are.
The Earth’s energy balance involves the absorption of incoming short-wave solar radiation and the emission of outgoing long-wave terrestrial radiation. Conduction and convection are non-radiative heat transfer mechanisms that move heat absorbed from radiation within the atmosphere and surface.

113. The term LASER stands for

The term LASER stands for

[amp_mcq option1=”Light Amplification by Stimulated Emission of Radiation” option2=”Light Amplification by Spontaneous Emission of Radiation” option3=”Light Amplification by Stimulated Emission of Rays” option4=”Light Amplification by Stimulated Energy of Radiation” correct=”option1″]

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The term LASER is an acronym for Light Amplification by Stimulated Emission of Radiation.
LASER is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The full form reflects the fundamental principle behind its operation.
The first working laser was demonstrated in 1960 by Theodore Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow, building on the principles established by Albert Einstein regarding stimulated emission.

114. If the amplitude of oscillation of a simple pendulum is very small, th

If the amplitude of oscillation of a simple pendulum is very small, then its time period of oscillation

  • 1. depends on the length of the pendulum, L
  • 2. depends on the acceleration due to gravity, g
  • 3. depends upon the mass of the bob of the pendulum, m
  • 4. does not depend upon the amplitude of the pendulum, A

Select the correct answer using the code given below.

[amp_mcq option1=”1, 2 and 3″ option2=”1, 2 and 4″ option3=”2, 3 and 4″ option4=”1 and 4 only” correct=”option2″]

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The time period of oscillation of a simple pendulum, when the amplitude is very small, depends on the length of the pendulum and the acceleration due to gravity, but not on the mass of the bob or the amplitude.
For small oscillations (amplitude A is very small), the formula for the time period (T) of a simple pendulum is given by T = 2π√(L/g), where L is the length of the pendulum and g is the acceleration due to gravity. This formula explicitly shows that the time period depends on L and g, but it does not contain the mass (m) of the bob or the amplitude (A). The condition of small amplitude is crucial for this simplified formula to hold, implying independence from amplitude in this specific case.
For larger amplitudes, the time period of a simple pendulum is slightly longer and does depend on the amplitude. However, the question specifically states “amplitude… is very small”, which validates the use of the small-angle approximation formula.

115. Lowering the atmospheric pressure on a liquid

Lowering the atmospheric pressure on a liquid

[amp_mcq option1=”increases the boiling point of the liquid” option2=”lowers the boiling point of the liquid” option3=”does not affect the boiling point of the liquid” option4=”increases the time required for it to boil” correct=”option2″]

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The correct answer is B) lowers the boiling point of the liquid.
Boiling point is defined as the temperature at which the vapor pressure of a liquid equals the surrounding atmospheric pressure. When the atmospheric pressure is lowered, the liquid needs to reach a lower vapor pressure to start boiling. Since vapor pressure increases with temperature, a lower required vapor pressure is achieved at a lower temperature. Therefore, lowering the atmospheric pressure on a liquid lowers its boiling point.
This principle is why water boils at a lower temperature at high altitudes (where atmospheric pressure is lower) than at sea level. For example, water boils at 100°C at standard atmospheric pressure (1 atm), but at approximately 93°C in Denver, Colorado (altitude ~1600m), and even lower on top of Mount Everest. Conversely, increasing the pressure (e.g., in a pressure cooker) increases the boiling point of water, allowing food to cook faster.

116. Which of the following statements about optical microscope is/are corr

Which of the following statements about optical microscope is/are correct?

  • 1. Both the eyepiece and objective of a microscope are convex lenses.
  • 2. The magnification of a microscope increases with increase in focal length of the objective.
  • 3. The magnification of a microscope depends upon the length of the microscope tube.
  • 4. The eyepiece of a microscope is a concave lens.

Select the correct answer using the code given below.

[amp_mcq option1=”1 and 3″ option2=”3 only” option3=”3 and 4″ option4=”1, 2 and 4″ correct=”option1″]

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The correct answer is A) 1 and 3.
Statement 1 is correct: In a standard compound optical microscope, both the objective lens (or lens system) and the eyepiece lens (or lens system) act as convex lenses to produce magnification. The objective creates a magnified real intermediate image, and the eyepiece magnifies this intermediate image to form a virtual final image.
Statement 2 is incorrect: The magnification of the objective lens is inversely proportional to its focal length. A shorter focal length objective provides higher magnification (and typically lower depth of field and working distance).
Statement 3 is correct: The overall magnification of a compound microscope is approximately the product of the magnification of the objective and the magnification of the eyepiece. The magnification provided by the objective is related to the distance between the objective and the intermediate image (which is determined by the microscope’s tube length) and the focal length of the objective. Thus, the length of the microscope tube affects the magnification.
Statement 4 is incorrect: As mentioned in statement 1, the eyepiece acts as a magnifying glass, which is achieved using a convex lens or a combination of lenses that function as a convex lens.
The total magnification of a compound microscope is typically calculated as M_total = M_objective × M_eyepiece. The objective magnification is often given by M_objective ≈ L / f_objective, where L is the mechanical tube length and f_objective is the focal length of the objective. This confirms that tube length (L) affects the magnification.

117. The optical phenomenon that is responsible for the propagation of ligh

The optical phenomenon that is responsible for the propagation of light signal through an optical fibre is

[amp_mcq option1=”interference” option2=”scattering” option3=”total internal reflection” option4=”refraction” correct=”option3″]

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The correct answer is C) total internal reflection.
Optical fibres work by guiding light along a core made of a material with a higher refractive index, surrounded by a cladding material with a lower refractive index. Light rays entering the core at appropriate angles strike the interface between the core and the cladding at an angle greater than the critical angle. When this condition is met, the light is completely reflected back into the core, a phenomenon called total internal reflection (TIR). This process repeats along the length of the fibre, allowing the light signal to propagate with minimal loss.
Refraction is the bending of light as it passes from one medium to another with a different refractive index, which is involved when light *enters* the fibre but not for its propagation *within* the fibre. Interference and scattering are optical phenomena but are not the primary principle responsible for guiding light in optical fibres; scattering, in fact, is a cause of signal loss.

118. The mass number of an element is NOT changed when it emits

The mass number of an element is NOT changed when it emits

[amp_mcq option1=”Alpha and Beta radiations only” option2=”Alpha and Gamma radiations only” option3=”Beta and Gamma radiations only” option4=”Alpha, Beta and Gamma radiations” correct=”option3″]

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The mass number (A) of an element is the total number of protons and neutrons in the nucleus.
– Alpha (α) decay: Emits a ⁴₂He nucleus. The mass number decreases by 4.
– Beta (β) decay (β⁻ or β⁺ or electron capture): In β⁻ decay, a neutron turns into a proton (A remains same, Z increases by 1). In β⁺ decay, a proton turns into a neutron (A remains same, Z decreases by 1). In electron capture, a proton captures an electron to become a neutron (A remains same, Z decreases by 1). In all Beta decay processes, the mass number does NOT change.
– Gamma (γ) decay: Emits a high-energy photon. This occurs when a nucleus transitions from a higher energy state to a lower energy state. Neither the atomic number (Z) nor the mass number (A) changes during gamma decay.
Therefore, the mass number is NOT changed when Beta and Gamma radiations are emitted.
Alpha decay changes both atomic number and mass number. Beta and Gamma decay do not change the mass number.
Radioactive decay processes result in the transformation of one atomic nucleus into another or into a lower energy state. The type of decay determines how the atomic number and mass number of the nucleus change.

119. Who among the following has coined the term ‘Quark’, the fundamental p

Who among the following has coined the term ‘Quark’, the fundamental particles that make up protons and neutrons in an atomic nucleus ?

[amp_mcq option1=”Richard Feynman” option2=”Murray Gell-Mann” option3=”Albert Einstein” option4=”Niels Bohr” correct=”option2″]

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The term ‘Quark’ for the fundamental particles that make up protons and neutrons was coined by American physicist Murray Gell-Mann in 1964. He proposed the quark model independently of George Zweig, who had called the particles “aces”. Gell-Mann chose the name “quark” from James Joyce’s novel “Finnegans Wake”.
Murray Gell-Mann proposed the quark model and named these fundamental particles ‘quarks’.
Protons and neutrons are baryons, which are composed of three quarks. For example, a proton is made of two up quarks and one down quark (uud), and a neutron is made of one up quark and two down quarks (udd).

120. Liquid water is denser than ice due to

Liquid water is denser than ice due to

[amp_mcq option1=”higher surface tension” option2=”hydrogen bonding” option3=”van der Waals forces” option4=”covalent bonding” correct=”option2″]

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Liquid water is denser than ice. This anomalous property is due to the unique structure formed by hydrogen bonding. In ice, water molecules form a rigid, open lattice structure (like a hexagonally ordered network) held together by hydrogen bonds. This structure is less compact than the arrangement of molecules in liquid water. In liquid water, while hydrogen bonds still exist, they are constantly breaking and reforming, allowing molecules to pack closer together, thus increasing the density compared to ice.
Hydrogen bonding in water is responsible for several of its anomalous properties, including the fact that solid water (ice) is less dense than liquid water.
Most substances contract and become denser when they solidify. Water expands and becomes less dense when it freezes. This property is crucial for life on Earth, as ice floats on water bodies, insulating the liquid water below and preventing lakes and rivers from freezing solid from the bottom up.
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