UPSC Science and Technology – Chapter 4: Physics in Everyday Life (26 MCQs)

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UPSC Science and Technology – Chapter 4: Physics in Everyday Life (26 MCQs) – 26 questions, subject: Science & Technology. Every question has the correct answer with a one-line explanation; tap "Show Answer". Free practice for TNPSC, UPSC, SSC, Bank and RRB exams – Shanmugam IAS Academy, Coimbatore.

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1.  

Since 2019, the kilogram has been defined through the:

Correct Answer: A [Planck constant]

Explanation:

Since 20 May 2019 the kilogram is defined by fixing the numerical value of the Planck constant.

2.  

A thermos flask keeps liquids hot mainly because:

Correct Answer: D [the vacuum stops conduction and convection and silvered walls cut radiation]

Explanation:

The vacuum between double walls blocks conduction and convection, and the silvered surfaces reflect radiant heat back.

3.  

Fish survive in a frozen lake in winter mainly because water:

Correct Answer: C [is densest at about 4 °C, so the water below the ice stays liquid]

Explanation:

anomalous expansion.

4.  

In which of the following does sound travel fastest?

Correct Answer: D [Steel]

Explanation:

Particles in solids are tightly bound, so sound travels several thousand metres a second in steel, faster than in water or air.

5.  

Clouds generally appear white because:

Correct Answer: B [their large water droplets scatter all colours of light about equally]

Explanation:

Droplets much larger than light's wavelength scatter all colours almost equally, so the mixed scattered light looks white.

6.  

Optical fibres carry light over long distances by:

Correct Answer: B [total internal reflection]

Explanation:

Light inside the fibre core strikes the boundary beyond the critical angle and is totally reflected, so it stays trapped.

7.  

Bats find their way in the dark by using:

Correct Answer: C [ultrasound]

Explanation:

Bats emit ultrasound above 20,000 Hz and locate objects from the returning echoes (echolocation).

8.  

Household electricity supply in India is:

Correct Answer: D [230 V, 50 Hz alternating current]

Explanation:

India's standard household supply is single-phase alternating current at 230 V and 50 Hz.

9.  

The working of electric generators is based on:

Correct Answer: C [electromagnetic induction]

Explanation:

discovered by Faraday.

10.  

Consider the following statements:

1. Rear-view mirrors in vehicles are convex mirrors.
2. Stars twinkle because of atmospheric refraction.
3. Sound can travel through a vacuum.

Which of the statements given above is/are correct?

Correct Answer: B [1 and 2 only]

Explanation:

Convex rear-view mirrors give a wider view and atmospheric refraction makes stars twinkle; sound cannot cross a vacuum.

11.  

Assertion (A): Red light is used for danger signals.

Reason (R): Red light is scattered the least by air and can be seen from a long distance.

Correct Answer: A [Both A and R are true, and R is the correct explanation of A]

Explanation:

Red has the longest visible wavelength, is scattered least by air and so is seen from far away, hence danger signals.

12.  

Which electromagnetic waves are used in TV remote controls?

Correct Answer: B [Infrared]

Explanation:

TV remotes send coded pulses of infrared light from an LED to a sensor on the set.

13.  

Police speed guns and Doppler weather radar work on the principle of:

Correct Answer: B [the Doppler effect]

Explanation:

Speed guns and Doppler radar measure the frequency shift of waves reflected from a moving object to find its speed.

14.  

Ice floats on water because:

Correct Answer: A [ice is less dense than water]

Explanation:

Water expands on freezing, so ice is less dense than water and the buoyant force keeps it afloat.

15.  

Seat belts in cars protect passengers mainly because of:

Correct Answer: D [the inertia of motion]

Explanation:

the body tends to keep moving when the car stops.

16.  

Which electromagnetic waves are used to treat cancer?

Correct Answer: A [Gamma rays]

Explanation:

High-energy gamma rays destroy cancer cells in radiotherapy, for example from cobalt-60 sources.

17.  

Arrange the following in chronological order:

1. Discovery of the Raman effect
2. First working laser
3. Galileo turns a telescope to the sky
4. Newton's Principia

Select the correct answer using the code given below:

Correct Answer: C [3-4-1-2]

Explanation:

1609, 1687, 1928, 1960.

18.  

A fuse wire in a household circuit should have:

Correct Answer: D [a low melting point so that it melts on overload]

Explanation:

A fuse wire has a low melting point, so excess current heats and melts it, breaking the circuit.

19.  

To hear a distinct echo in air, the reflecting surface must be at least about how far from the listener?

Correct Answer: B [17 m]

Explanation:

sound at about 343 m/s covers about 34 m there and back in 0.1 second, the time the ear retains a sound.

20.  

National Science Day (28 February) marks the discovery of:

Correct Answer: B [the Raman effect]

Explanation:

discovered in 1928.

21.  
UPSC Prelims 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.

Correct Answer: C [1 and 3 only]

Explanation:

the hole and the lid weight set the pressure and so the boiling point.

22.  
UPSC Prelims 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 a longer lifespan 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.

Correct Answer: C [1 and 3 only]

Explanation:

Sodium lamps emit all around and give near-monochromatic yellow light; statement 2 is wrong because LEDs last longer.

23.  
UPSC Prelims 2013

Ball bearings are used in bicycles, cars, etc. because

Correct Answer: C [The effective area of contact between the wheel and axle is reduced]

Explanation:

rolling replaces sliding and friction falls.

24.  
UPSC Prelims 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?

Correct Answer: C [1, 2 and 4]

Explanation:

the larger size of the Sun at dusk is a visual illusion; its red colour (scattering) and the twinkling of stars (atmospheric refraction) are atmospheric effects on light.

25.  
UPSC Prelims 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 code given below:

Correct Answer: D [1, 2 and 3]

Explanation:

all three act inside each raindrop.

26.  
UPSC Prelims 2013

The known forces of nature can be divided into four classes, viz., gravity, electromagnetism, weak nuclear force and strong nuclear force. With reference to them, which one of the following statements is not correct?

Correct Answer: A [Gravity is the strongest of the four]

Explanation:

(a) Correct answer – this statement is not correct; gravity is the weakest.

➤ Full notes, maps, tables, a reason for every option and Mains PYQs – U17 · Science and Technology (UPSC book, ₹249): www.shanmugamiasacademy.in/study-materials/upsc-science-technology

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