11. In which of the following respects are light waves different from sound waves?
- Light waves are electromagnetic but sound waves are not.
- Light waves can travel through water but sound waves cannot.
- Light travels with the same speed in all media.
- Light waves produce interference but sound waves do not.
Select the correct option from the codes given below:
[A] Only 1
[B] Only 1, 2 & 3
[C] Only 1 & 4
[D] None
Show Answer
Correct Answer: A [Only 1]
Notes:
Only statement 1 is correct; light waves are electromagnetic, while sound waves are mechanical. Statement 2 is incorrect; both light and sound can travel through water. Statement 3 is incorrect; light’s speed changes with medium. Statement 4 is incorrect; both light and sound waves can show interference under appropriate conditions.
12. Consider the following phenomena affecting the propagation of radio waves in the Earth's atmosphere:
- Reflection
- Refraction
- Diffraction
- Absorption
Which of the above phenomena influence radio wave propagation?
[A] 1, 2, 3 and 4
[B] Only 1, 2 and 3
[C] Only 1, 3 and 4
[D] Only 1, 2 and 4
Show Answer
Correct Answer: A [1, 2, 3 and 4]
Notes:
All four phenomena — reflection, refraction, diffraction, and absorption — affect radio wave propagation in the Earth’s atmosphere. Reflection and refraction alter path and speed, diffraction allows bending around obstacles, while absorption occurs mainly in the ionosphere, impacting signal strength. Each plays a significant role in radio communication and signal transmission.
13. Consider the following statements regarding the apparent twinkling of stars near the horizon:
- The atmosphere is denser at the horizon, causing increased twinkling of stars close to it.
- The energy output from stars varies frequently, leading to enhanced twinkling near the horizon.
Which of the above statements is/are correct?
[A] Only 1 is correct
[B] Only 2 is correct
[C] Only 1 is correct
[D] Both 1 and 2 are correct
Show Answer
Correct Answer: C [Only 1 is correct]
Notes:
Stars twinkle more near the horizon because their light passes through a denser and more extensive part of the Earth's atmosphere, which refracts the light more strongly, creating the twinkling effect. The variation in a star's intrinsic energy output does not cause twinkling; therefore, only statement 1 is correct, not statement 2.
14. Consider the following statements:
- Neutrinos do not carry an electric charge but have mass.
- Neutrinos travel faster than light.
Which of the above statements is / are correct?
[A] Only 1
[B] Only 2
[C] Neither 1 nor 2
[D] Both 1 and 2
Show Answer
Correct Answer: C [Neither 1 nor 2]
Notes:
Statement 1 is correct, as neutrinos are electrically neutral particles with a very small but nonzero mass. Statement 2 is incorrect because, according to current scientific understanding, no known particle, including neutrinos, can travel faster than the speed of light in a vacuum.
15. Consider the following statements:
- Sagittarius A* is a supermassive black hole at the center of the Andromeda.
- Event horizon is the point of no return beyond which electromagnetic radiation gets dragged into oblivion.
- The wormhole is a passage through space-time.
Which of the statements given above are correct?
[A] Only 1 & 2
[B] Only 2 & 3
[C] Only 1 & 3
[D] 1, 2 & 3
Show Answer
Correct Answer: B [Only 2 & 3]
Notes:
- Sagittarius A* is a supermassive black hole at the center of our galaxy i.e., the Milky Way. It is located near the border of the constellations Sagittarius and Scorpius.
- There’s a boundary at the edge of a black hole called the event horizon, which is the point of no return any light or matter that crosses that boundary is sucked into the black hole. It would need to travel faster than the speed of light to escape, which is impossible. It is the point of no return beyond which anything stars, planets, gas, dust and all forms of electromagnetic radiation gets dragged into oblivion.
- The wormhole theory postulates that a theoretical passage through space-time could create shortcuts for long journeys across the universe.
16. Consider the following statements:
- All the weather phenomena like rainfall, fog and hailstorm occur in stratosphere.
- Stratosphere also contains a layer of ozone gas.
Which of the above is / are correct?
[A] Only 1
[B] Only 2
[C] Both 1 and 2
[D] None of the above
Show Answer
Correct Answer: A [Only 1]
Notes:
Troposphere is the most important layer of the atmosphere. Its average height is 13 km. The air we breathe exists here. Almost all the weather phenomena like rainfall, fog and hailstorm occur in this layer. Above the troposphere lies the stratosphere. It extends up to a height of 50 km. This layer is almost free from clouds and associated weather phenomenon, making conditions most ideal for flying aeroplanes. One important feature of stratosphere is that it contains a layer of ozone gas.
17. Consider the following statements:
- The uppermost layer of atmosphere is Ionosphere.
- Light gases like helium and hydrogen float into space from exosphere.
Which of the above is / are correct?
[A] Only 1
[B] Only 2
[C] Both 1 and 2
[D] None of the above
Show Answer
Correct Answer: B [Only 2]
Notes:
In thermosphere temperature rises very rapidly with increasing height. Ionosphere is a part of this. It extends between 80-400 km. This layer helps in radio transmission. In fact, radio waves transmitted from the earth are reflected back to the earth by this layer. The upper most layer of the atmosphere is known as exosphere. This layer has very thin air. Light gases like helium and hydrogen float into space from here.
18. Consider the following statements about the IceCube Neutrino Observatory:
- The IceCube telescope is a powerful tool to search for dark matter.
- IceCube studies the neutrons.
- The IceCube Neutrino Observatory is constructed at the Amundsen–Scott South Pole Station in Antarctica.
Which of the statements given above is/are correct?
[A] Only 3
[B] Only 1 and 2
[C] 1, 2 and 3
[D] Only 1 and 3
Show Answer
Correct Answer: D [Only 1 and 3]
Notes:
Statements 1 and 3 are correct. The IceCube telescope is a powerful detector that investigates dark matter and is located at the Amundsen–Scott South Pole Station in Antarctica. Statement 2 is incorrect as IceCube studies neutrinos, not neutrons. It detects astrophysical neutrinos, not other subatomic particles such as neutrons.
19. Consider the following statements about a Luminous object :
- It is an object which does not give its own light.
- They act as the sources of light.
Which of the above is / are correct?
[A] Only 1
[B] Only 2
[C] Both 1 and 2
[D] None of the above
Show Answer
Correct Answer: B [Only 2]
Notes:
An object with gives out its own light is called a luminous object. A Luminous object is a source of light. A luminous object can be seen because the light given out by it enters our eyes. An object which does not give out its own light is called a non-luminous object. A non-luminous object can be seen only when light coming from a luminous object falls on it. We can see the non-luminous object because it reflects light (received from a luminous object) into our eyes.
20. Consider the following statements regarding magnetic materials:
- They are not attracted by a magnet.
- They can be converted into magnets.
Which of the above statement(s) is/are correct?
[A] Only 2
[B] Only 1
[C] Both 1 and 2
[D] None of the above
Show Answer
Correct Answer: A [Only 2]
Notes:
Magnetic materials, such as iron, steel, nickel and cobalt, are attracted by magnets and can also be converted into magnets. Non-magnetic materials are not attracted by a magnet and cannot be converted into magnets. Hence, only statement 2 is correct; statement 1 incorrectly describes magnetic materials as not attracted by magnets.
