41. In context with historical figures, consider the following pair:
| Names |
Achievements |
| 1. Marie Curie |
First woman to win a Nobel Prize in Physics |
| 2. Albert Einstein |
Developed the Theory of General Relativity |
| 3. Galileo Galilei |
Laid the foundation for classical mechanics and gravitational theory |
| 4. Isaac Newton |
Referred to as the father of modern observational astronomy |
How many of the above pairs are correct?
[A] Only one
[B] Only two
[C] Only three
[D] All four
Show Answer
Correct Answer: B [Only two]
Notes:
- Marie Curie was the first woman to win a Nobel Prize in Physics: This is correct. She won the Nobel Prize in Physics in 1903.
- Albert Einstein developed the theory of general relativity, which revolutionized our understanding of gravity: This is correct. He published this theory in 1915.
- Galileo Galilei is often referred to as the father of modern observational astronomy. His telescope observations laid the groundwork for modern astronomy.
- Isaac Newton’s work laid the foundation for classical mechanics and gravitational theory. His work, including the laws of motion, is fundamental to physics.
42. Consider the following statements about nuclear fusion:
- Nuclear fusion happens when two heavy atomic nuclei merge to form a lighter nucleus, releasing energy.
- It requires extremely high temperatures to overcome electrostatic repulsion between nuclei.
- Fusion energy produces minimal long-lived radioactive waste, unlike fission.
How many of the above statements are incorrect?
[A] Only one
[B] Only two
[C] All three
[D] None
Show Answer
Correct Answer: B [Only two]
Notes:
- Nuclear fusion happens when two heavy atomic nuclei merge to form a lighter nucleus, releasing energy. Incorrect: Nuclear fusion involves the merging of light atomic nuclei (such as hydrogen isotopes deuterium and tritium) to form a heavier nucleus (helium), releasing a vast amount of energy. Unlike nuclear fission, fusion does not involve heavy nuclei.
- It requires extremely high temperatures to overcome electrostatic repulsion between nuclei. Correct: Fusion requires extremely high temperatures (over 100 million Kelvin) to overcome the Coulomb barrier, which is the electrostatic repulsion between positively charged nuclei.
- Fusion energy produces minimal long-lived radioactive waste, unlike fission. Incorrect: Unlike nuclear fission, fusion does not generate long-lived radioactive waste. The main byproduct of fusion is helium, which is non-radioactive. Although fusion reactions involving tritium can produce some radioactive materials, their half-life is much shorter than that of fission waste.
43. Consider the following statements regarding the impact of iron opacity on stellar models:
- Higher opacity values increase the rate of neutrino production in the solar core.
- Iron opacity discrepancies challenge existing solar models’ predictions of element abundances.
- The radiation-convection zone boundary in the sun is a key region where iron opacity is tested.
- Inaccurate opacity data can mislead predictions about stellar evolution and galactic structure.
Which of the above statements is / are correct?
[A] Only 1 and 2
[B] 2, 3 and 4
[C] 1, 3 and 4
[D] All of the statements
Show Answer
Correct Answer: B [2, 3 and 4]
Notes:
- Neutrino production is driven by nuclear fusion reactions in the core, not by opacity. Thus, changing opacity values does not directly affect neutrino production.
- The discrepancies caused by iron opacity challenge our understanding of solar models, suggesting that element abundances may not be as predicted.
- The radiation-convection zone boundary in the sun is indeed where iron opacity is tested, allowing us to understand how energy is transported throughout the star.
- Opacity is crucial in modelling the structure and evolution of stars. Inaccurate opacity data can lead to erroneous predictions about galaxy structure and overall universe evolution.
44. Which of the following Nobel Prize–winning contributions are correctly matched with their respective scientists?
- Max Planck → Quantum theory (1918)
- Niels Bohr → Structure of atoms (1922)
- Richard Feynman → Quantum electrodynamics (1965)
Select the correct option from the codes given below:
[A] Only 1 & 2
[B] Only 2 & 3
[C] Only 1 & 3
[D] 1, 2 & 3
Show Answer
Correct Answer: D [1, 2 & 3]
Notes:
Max Planck was awarded the Nobel Prize in 1918 for quantum theory. Niels Bohr received the Nobel Prize in 1922 for his work on atomic structure. Richard Feynman, with Schwinger and Tomonaga, received the Nobel Prize in 1965 for their fundamental work in quantum electrodynamics. All statements are correct.
45. Why do sharp knives cut better than blunt ones?
[A] Sharp edges increase tensile strength of blade
[B] Sharp edges reduce work done against gravity
[C] Sharp edges increase pressure by reducing contact area
[D] Sharp edges reduce friction during cutting
Show Answer
Correct Answer: C [Sharp edges increase pressure by reducing contact area]
Notes:
Sharp knives concentrate force on a smaller area, increasing pressure, thus making cutting easier. This is a direct application of Pressure = Force/Area. The higher pressure allows the blade to break material bonds more efficiently compared to blunt knives with larger contact areas.
46. Why do ears sometimes “pop” when climbing mountains or during flights?
[A] Due to rapid increase in gravitational pull
[B] Blood pressure increases with altitude
[C] Pressure difference between inner ear and outside air
[D] Sound waves travel faster in low pressure
Show Answer
Correct Answer: C [Pressure difference between inner ear and outside air]
Notes:
Ear “popping” occurs due to pressure difference between the inner ear and outside air. The Eustachian tubes open to equalize pressure across the eardrum, typically during altitude changes such as in airplanes or while climbing mountains. This is a normal physiological response.
47. Why does a hydrometer float higher in pure milk than diluted milk?
[A] Volume of hydrometer changes with liquid
[B] Pressure at vessel bottom stays constant
[C] Buoyant force depends on density of liquid
[D] Surface tension changes with purity
Show Answer
Correct Answer: C [Buoyant force depends on density of liquid]
Notes:
Pure milk’s higher density increases buoyant force, making hydrometer float higher. Archimedes’ principle relates liquid density to floating objects’ positions. In diluted milk, lower density provides less buoyant force, causing hydrometer to sink deeper. Hydrometers measure specific gravity using this physical property.
48. Why do heavy machinery gear oils have a high viscosity index?
[A] To remain stable in viscosity across a wide temperature range
[B] To increase density of oil at high temperature
[C] To reduce friction by becoming thinner at high temperature
[D] To prevent surface tension from collapsing under load
Show Answer
Correct Answer: A [To remain stable in viscosity across a wide temperature range]
Notes:
Oils with high viscosity index retain consistent thickness and lubricating property at various temperatures, ensuring machinery protection during cold starts and high loads. This prevents wear and maintains performance.
49. Why are electric power lines transmitted at very high voltages?
[A] Because insulation is stronger at high voltage
[B] Because transformers cannot work at low voltage
[C] Because high voltage reduces current and power loss
[D] Because high voltage increases power carried by line
Show Answer
Correct Answer: C [Because high voltage reduces current and power loss]
Notes:
Transmitting at high voltages reduces current for given power (P = VI), thus reducing resistive losses (I²R). This improves efficiency in long-distance transmission. Transformers enable voltage changes for safe distribution. Lower losses also reduce costs and heating of wires.
50. What is the focal length of a plane mirror?
[A] +1 cm
[B] 2 cm
[C] -1 cm
[D] Infinity
Show Answer
Correct Answer: D [Infinity]
Notes:
The focal length of a plane mirror is infinity because its radius of curvature is infinite; it does not converge or diverge incident rays and always forms virtual images. Unlike spherical mirrors, its reflecting surface is flat.
