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Q1Science·Physics in Everyday LifePYQ 2026
Which of the following statements with regard to Black Boxes used in modern aircrafts is/are correct?
1. They carry a beacon emitting red light pulses to facilitate underwater detection.
2. They record both the cockpit voice and flight data.
3. Their memory units are made using either stainless steel or titanium.
Select the answer using the code given below:
- A1 only
- B2 and 3 onlyCorrect
- C1 and 2 only
- D1, 2 and 3
Why the other options are incorrect
- Option A
Statement 1 is false. An underwater locator beacon sends acoustic pulses that search equipment can detect; it does not locate a submerged recorder by emitting red light. The orange exterior helps visual identification, which is a different function.
- Option C
Statement 2 is correct, but statement 1 is not: underwater recovery relies on a sound-emitting beacon. This option also omits the protective steel or titanium enclosure referred to by statement 3.
- Option D
The red-light assertion in statement 1 makes this option incorrect. Modern recorders preserve audio and flight data in protected electronic memory, and the underwater beacon emits sound rather than red pulses.
Q2Science·Physics in Everyday LifePYQ 2022
Which one of the following is the context in which the term 'qubit' is mentioned?
- ACloud Services
- BQuantum ComputingCorrect
- CVisible Light Communication Technologies
- DWireless Communication Technologies
Explanation
Correct. A qubit (quantum bit) is the basic unit of information in quantum computing, analogous to a classical bit but capable of existing in superposition states.
Why the other options are incorrect
- Option A
Cloud services use classical bits for data processing and storage, not qubits.
- Option C
Visible light communication (Li-Fi) uses modulated light signals and has no connection to qubits.
- Option D
Wireless communication technologies such as Wi-Fi and 5G rely on classical electromagnetic signals, not quantum bits.
Q3Science·Physics in Everyday LifePYQ 2021
In a pressure cooker, the temperature at which the food is cooked depends mainly upon which of the following?
1. Area of the hole in the lid
2. Temperature of the flame
3. Weight of the lid
Select the correct answer using the code given below.
- A1 and 2 only
- B2 and 3 only
- C1 and 3 onlyCorrect
- D1, 2 and 3
Explanation
Correct. The cooking temperature inside a pressure cooker depends on the internal steam pressure, which is governed by the area of the vent hole (through which steam escapes) and the weight of the lid/whistle (which determines the pressure needed to release steam).
Why the other options are incorrect
- Option A
The temperature of the flame affects how fast the cooker reaches cooking temperature, but the final cooking temperature is determined by the pressure inside, which depends on the hole area and lid weight.
- Option B
Flame temperature governs heating rate, not the equilibrium cooking temperature; it does not control the internal pressure.
- Option D
Flame temperature only affects the time taken to build pressure, not the final cooking temperature achieved.
Q4Science·Physics in Everyday LifePYQ 2021
With reference to street-lighting, how do sodium lamps differ from LED lamps?
1. Sodium lamps produce light in 360 degrees but it is not so in the case of LED lamps.
2. As street-lights, sodium lamps have longer life span than LED lamps.
3. The spectrum of visible light from sodium lamps is almost monochromatic while LED lamps offer significant colour advantages in street-lighting.
Select the correct answer using the code given below.
- A3 only
- B2 only
- C1 and 3 onlyCorrect
- D1, 2 and 3
Explanation
Correct. Sodium lamps emit omnidirectional (360°) light requiring reflectors, while LEDs are directional. Sodium lamps produce near-monochromatic yellow light, whereas LEDs can produce a wide colour spectrum. Statement 2 is false because LEDs outlast sodium lamps.
Why the other options are incorrect
- Option A
Statement 1 is also correct — sodium lamps emit light omnidirectionally (360°) while LEDs are directional.
- Option B
LED lamps have a significantly longer lifespan than sodium lamps, making statement 2 incorrect.
- Option D
Statement 2 is incorrect. LEDs typically last 50,000-100,000 hours compared to about 24,000 hours for sodium lamps.
Q5Science·Physics in Everyday LifePYQ 2017
Organic Light Emitting Diodes (OLEDs) are used to create digital display in many devices. What are the advantages of OLED displays over Liquid Crystal displays?
1. OLED displays can be fabricated on flexible plastic substrates.
2. Roll-up displays embedded in clothing can be made using OLEDs.
3. Transparent displays are possible using OLEDs.
Select the correct answer using the code given below.
- A1 and 3 only
- B2 only
- C1, 2 and 3Correct
- DNone of the above statements is correct
Explanation
Correct. OLEDs are organic compounds that emit light when current passes through them. They can be deposited on flexible plastic substrates (1), enabling roll-up wearable displays (2), and since they do not need a backlight, transparent displays are feasible (3).
Why the other options are incorrect
- Option A
Statement 2 is also correct — OLEDs can be printed on flexible substrates thin enough to be woven into clothing for roll-up displays.
- Option B
Statements 1 and 3 are also correct; OLEDs offer flexibility and transparency as advantages over LCDs.
- Option D
All three statements are factually accurate advantages of OLED technology over LCD.
Q6Science·Physics in Everyday LifePYQ 2013
Ball bearings are used in bicycles, cars, etc., because:
- AThe actual area of contact between the wheel and axle is increased
- BThe effective area of contact between the wheel and axle is increased
- CThe effective area of contact between the wheel and axle is reducedCorrect
- DNone of the statements is correct
Explanation
Correct. Ball bearings convert sliding friction into rolling friction by reducing the effective area of contact between the wheel and the axle, thereby minimising energy loss.
Why the other options are incorrect
- Option A
Increasing actual contact area would increase friction, which is the opposite of what ball bearings are designed to do.
- Option B
Increasing effective contact area would raise friction. Ball bearings work by minimising, not maximising, surface contact.
- Option D
Statement (c) is correct, so this option is wrong.
Q7Science·Physics in Everyday LifePYQ 2013
Consider the following phenomena:
1. Size of the sun at dusk
2. Colour of the sun at dawn
3. Moon being visible at dawn
4. Twinkle of stars in the sky
5. Polestar being visible in the sky
Which of the above are optical illusions?
- A1, 2 and 3
- B3, 4 and 5
- C1, 2 and 4Correct
- D2, 3 and 5
Explanation
Correct. The sun appears larger at dusk due to the 'moon illusion' effect near the horizon, its reddish colour at dawn is caused by atmospheric scattering (Rayleigh scattering), and the twinkling of stars is caused by atmospheric refraction — all are optical illusions.
Why the other options are incorrect
- Option A
The moon being visible at dawn is a real phenomenon, not an optical illusion; it is physically present above the horizon.
- Option B
The moon at dawn and the Polestar being visible are real observations, not illusions caused by atmospheric refraction.
- Option D
The Polestar being visible is a genuine astronomical fact related to Earth's axial alignment, not an illusion.
Q8Science·Physics in Everyday LifePYQ 2013
Rainbow is produced when sunlight falls on drops of rain. Which of the following physical phenomena are responsible for this?
1. Dispersion
2. Refraction
3. Internal reflection
Select the correct answer using the codes given below.
- A1 and 2 only
- B2 and 3 only
- C1 and 3 only
- D1, 2 and 3Correct
Explanation
Correct. A rainbow forms because sunlight entering a raindrop is refracted, dispersed into its component colours, and then internally reflected before exiting the drop and reaching the observer.
Why the other options are incorrect
- Option A
Internal reflection inside the raindrop is also essential for directing the dispersed light back towards the observer.
- Option B
Dispersion is the key phenomenon that splits white light into its constituent colours; omitting it is incorrect.
- Option C
Refraction at the air-water interface bends the light and enables dispersion; all three phenomena work together.
Q9Science·Physics in Everyday LifePYQ 2011
The surface of a lake is frozen in severe winter, but the water at its bottom is still liquid. What is the reason?
- AIce is a bad conductor of heat
- BSince the surface of the lake is at the same temperature as the air, no heat is lost
- CThe density of water is maximum at 4°CCorrect
- DNone of the statements (a), (b) and (c) given is correct
Explanation
Correct. Water has maximum density at 4°C. As surface water cools below 4°C it becomes lighter and stays on top, eventually freezing, while the denser 4°C water sinks and remains liquid at the bottom.
Why the other options are incorrect
- Option A
While ice does insulate, this is a secondary factor. The primary reason the bottom stays liquid is the anomalous expansion of water.
- Option B
The surface being at air temperature does not explain why the bottom remains liquid; heat is still being lost at the surface.
- Option D
Statement (c) is the correct explanation, so this option is wrong.
Q10Science·Physics in Everyday LifePYQ 2010
What is the principle by which a cooling system (radiator) in a motor car works?
- AConduction only
- BConvectionCorrect
- CRadiation only
- DBoth conduction and radiation
Explanation
Correct. A car radiator works primarily on the principle of convection — hot coolant circulates from the engine to the radiator where moving air carries away heat through convective heat transfer.
Why the other options are incorrect
- Option A
Conduction alone cannot circulate coolant through the system; bulk fluid movement is needed.
- Option C
Radiation contributes very little compared to the convective transfer of heat by the flowing coolant and airstream.
- Option D
While conduction occurs at metal surfaces, the dominant working principle is convection, not a combination of conduction and radiation.
Q11Science·Physics in Everyday LifePYQ 2009
Which one of the following types of waves are used in a night vision apparatus?
- ARadio waves
- BInfrared wavesCorrect
- CUltraviolet waves
- DMicrowaves
Explanation
Correct. Night vision devices detect infrared radiation emitted by warm objects and convert it into a visible image, allowing vision in complete darkness.
Why the other options are incorrect
- Option A
Radio waves have very long wavelengths and are used for communication, not for imaging warm objects at night.
- Option C
Ultraviolet waves are higher in energy than visible light and are not emitted in significant amounts by warm objects at night.
- Option D
Microwaves are used in radar and cooking, not in night vision equipment.
Q12Science·Physics in Everyday LifePYQ 2008
Assertion (A): Radio waves bend in a magnetic field.
Reason (R): Radio waves are electromagnetic in nature.
- ABoth A and R are individually true and R is the correct explanation of A
- BBoth A and R are individually true but R is not the correct explanation of A
- CA is false but R is trueCorrect
- DA is false and R is false
Explanation
Correct. Radio waves, being electromagnetic waves, do not carry electric charge and therefore are not deflected by a magnetic field. However, the reason is true — radio waves are indeed electromagnetic in nature.
Why the other options are incorrect
- Option A
The assertion is false — electromagnetic waves do not bend in a magnetic field, so A and R cannot both be true with R explaining A.
- Option B
Since A is false, this combination is not possible.
- Option D
The reason is true; radio waves are electromagnetic waves. Only the assertion is false.