Physics Questions and Answers

Q: Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R.Assertion A: Silver is not used to make electric wires.Reason R: Silver is a bad conductor.In the light of the above statements, choose the most appropriate answer from the options given below:

The answer is A is correct but R is not correct.The Assertion is true: silver is not used for ordinary electric wiring. The Reason is false, because silver is the best electrical conductor of all metals, slightly better than copper.Silver is avoided because it is far too expensive (and soft) for wiring; copper conducts almost as well at a fraction of the cost, and aluminium is used for overhead lines because it is light. So the real reason is cost, not poor conductivity.

Q: Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R.Assertion A: Presbyopia is a defect to eyes due to ageing. It is usually due to decrease in the power of accommodation of the eye.Reason R: Presbyopia can be treated using bifocal lens consists convex lens in upper portion to facilitate distant vision and concave lens in lower portion to facilitate near vision.In the light of the above statements, choose the most appropriate answer from the options given below:

The answer is A is correct but R is not correct.The Assertion is true: presbyopia develops with age as the eye lens loses flexibility and the ciliary muscles weaken, so the power of accommodation falls and near objects become hard to see.The Reason has the bifocal lens upside down. In a bifocal lens the upper part is a concave lens for distant vision and the lower part is a convex lens for near vision (reading). The Reason swaps them, so it is incorrect.

Q: Consider the following sentences -a. Uniform motion of objects can be shown through graphs.b. Uniform motion of objects cannot be shown through graphs.c. Non-Uniform motion of objects cannot be shown through graphs.d. Non-Uniform motion of objects can be shown through graphs.e. Velocity of an object is the displacement covered per unit time.Choose the most appropriate answer from the options given below:

The correct statements are a, d and e.Both uniform and non-uniform motion can be shown on graphs. Uniform motion gives a straight-line distance-time graph, and non-uniform motion gives a curved one. So a and d are true, and b and c, which deny this, are false.Statement e is the definition of velocity: the displacement of an object per unit time, in a given direction.Every option other than D includes b or c, so they are wrong.

Q: Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R.Assertion A: Reflecting surfaces of all types obey the laws of reflection. The refracting surfaces obey the laws of refraction.Reason R: Refractive index of a transparent medium is the ratio of the speed of light in vaccum to that in the medium.In the light of the above statements, choose the most appropriate answer from the options given below:

The answer is Both A and R are correct but R is not the correct explanation of A.The Assertion is true: every reflecting surface, plane or curved, obeys the laws of reflection, and every refracting surface obeys the laws of refraction.The Reason is also true: the absolute refractive index of a medium is the speed of light in vacuum divided by its speed in that medium. But a definition of refractive index does not explain why surfaces obey the laws of reflection and refraction, so R is not the explanation of A.

Q: The valence electron of the impurity atom that is to be added to germanium crystal so as to make it a n-type semiconductor is

The impurity atom must have 5 valence electrons.Germanium is in group 14 and has four valence electrons, each shared in a covalent bond with a neighbouring atom. A pentavalent dopant such as phosphorus, arsenic or antimony uses four of its five electrons in those bonds, and the fifth is only loosely held, so it is easily freed to conduct. Because the extra carriers are negative electrons, the crystal becomes an n-type semiconductor.A trivalent impurity (3 valence electrons, such as boron or indium) leaves a hole in one bond and gives a p-type semiconductor. An atom with 4 valence electrons simply fits into the lattice like germanium itself, and 6 is not the valence of any standard dopant for germanium.

Q: A particle executes S.H.M. The acceleration of the particle is maximum

The acceleration is maximum at the extreme position.In simple harmonic motion the acceleration is proportional to the displacement from the mean position and directed towards it:\[ a = -\omega^{2} x \]The displacement is largest, equal to the amplitude, at either extreme, so the acceleration is largest there too. At the mean position x = 0, so the acceleration is zero, while the speed is at its maximum.So 'at mean position' confuses acceleration with velocity, the midway point gives only half the maximum value, and the acceleration is clearly not the same everywhere because it changes with x.

Q: The velocity of sound is maximum in

Sound travels fastest in a metal.Sound is a mechanical wave and needs a medium. Its speed depends on how stiff the medium is compared with its density, and solids are far stiffer than liquids or gases. Typical values are about 5,000 to 6,000 m/s in steel, about 1,500 m/s in water and about 340 m/s in air.So water is slower than metal and air slower still. In a vacuum there are no particles to carry the vibration, so sound cannot travel at all and its speed there is not a maximum but zero.

Q: When the frequency of an electromagnetic wave and ultrasonic wave are same, then

The wavelength of the electromagnetic wave will be more.For any wave, speed = frequency \(\times\) wavelength, so at the same frequency the wave that travels faster has the longer wavelength:\[ \lambda = \frac{v}{f} \]Electromagnetic waves travel at about \(3 \times 10^{8}\) m/s in air, while ultrasonic waves are sound and travel at only about 340 m/s. So the electromagnetic wavelength is roughly a million times longer.The wavelengths cannot be equal because the speeds differ, and the options making the ultrasonic wavelength larger or the electromagnetic one smaller say the opposite of the result.

Q: A convex lens of focal length 40 cm is in contact with a concave lens of focal length 25 cm. The power of the combination is

The power of the combination is -1.5 D.Power in dioptres is the reciprocal of the focal length in metres, positive for a convex lens and negative for a concave lens. For lenses in contact, the powers add:\[ \begin{aligned} P &= \frac{1}{0.40} + \left(-\frac{1}{0.25}\right) \\ &= 2.5 - 4 = -1.5\ \text{D} \end{aligned} \]+1.5 D ignores the fact that the stronger concave lens wins, and ±6.5 D comes from adding the two powers as if both had the same sign.

Q: Which of the following has the least wavelength?

X-rays have the least wavelength among these.In order of decreasing wavelength the electromagnetic spectrum runs: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays. Radio waves can be metres to kilometres long, microwaves millimetres to centimetres, ultraviolet about 10 to 400 nm, and X-rays roughly 0.01 to 10 nm.So of the four options X-rays are shortest; ultraviolet is next, and microwaves and radio waves are far longer.

51.

Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R.

Assertion A: Silver is not used to make electric wires.
Reason R: Silver is a bad conductor.

In the light of the above statements, choose the most appropriate answer from the options given below:

A.Both A and R are correct and R is the correct explanation of A.
B.Both A and R are correct but R is not the correct explanation of A.
C.A is correct but R is not correct.
D.A is not correct but R is correct.

Exam Year(s)

RSMSSB - 2026, RSMSSB Mahila Supervisor - 2026,

Answer: C

The answer is A is correct but R is not correct.

The Assertion is true: silver is not used for ordinary electric wiring. The Reason is false, because silver is the best electrical conductor of all metals, slightly better than copper.

Silver is avoided because it is far too expensive (and soft) for wiring; copper conducts almost as well at a fraction of the cost, and aluminium is used for overhead lines because it is light. So the real reason is cost, not poor conductivity.

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52.

Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R.

Assertion A: Presbyopia is a defect to eyes due to ageing. It is usually due to decrease in the power of accommodation of the eye.
Reason R: Presbyopia can be treated using bifocal lens consists convex lens in upper portion to facilitate distant vision and concave lens in lower portion to facilitate near vision.

In the light of the above statements, choose the most appropriate answer from the options given below:

A.Both A and R are correct and R is the correct explanation of A.
B.Both A and R are correct but R is not the correct explanation of A.
C.A is correct but R is not correct.
D.A is not correct but R is correct.

Exam Year(s)

RSMSSB - 2026, RSMSSB Mahila Supervisor - 2026,

Answer: C

The answer is A is correct but R is not correct.

The Assertion is true: presbyopia develops with age as the eye lens loses flexibility and the ciliary muscles weaken, so the power of accommodation falls and near objects become hard to see.

The Reason has the bifocal lens upside down. In a bifocal lens the upper part is a concave lens for distant vision and the lower part is a convex lens for near vision (reading). The Reason swaps them, so it is incorrect.

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53.

Consider the following sentences -

a. Uniform motion of objects can be shown through graphs.
b. Uniform motion of objects cannot be shown through graphs.
c. Non-Uniform motion of objects cannot be shown through graphs.
d. Non-Uniform motion of objects can be shown through graphs.
e. Velocity of an object is the displacement covered per unit time.

Choose the most appropriate answer from the options given below:

A.a, b and c
B.b, c and d
C.c, d and e
D.a, d and e

Exam Year(s)

RSMSSB - 2026, RSMSSB Mahila Supervisor - 2026,

Answer: D

The correct statements are a, d and e.

Both uniform and non-uniform motion can be shown on graphs. Uniform motion gives a straight-line distance-time graph, and non-uniform motion gives a curved one. So a and d are true, and b and c, which deny this, are false.

Statement e is the definition of velocity: the displacement of an object per unit time, in a given direction.

Every option other than D includes b or c, so they are wrong.

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54.

Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R.

Assertion A: Reflecting surfaces of all types obey the laws of reflection. The refracting surfaces obey the laws of refraction.
Reason R: Refractive index of a transparent medium is the ratio of the speed of light in vaccum to that in the medium.

In the light of the above statements, choose the most appropriate answer from the options given below:

A.Both A and R are correct and R is the correct explanation of A.
B.Both A and R are correct but R is not the correct explanation of A.
C.A is correct but R is not correct.
D.A is not correct but R is correct.

Exam Year(s)

RSMSSB - 2026, RSMSSB Mahila Supervisor - 2026,

Answer: B

The answer is Both A and R are correct but R is not the correct explanation of A.

The Assertion is true: every reflecting surface, plane or curved, obeys the laws of reflection, and every refracting surface obeys the laws of refraction.

The Reason is also true: the absolute refractive index of a medium is the speed of light in vacuum divided by its speed in that medium. But a definition of refractive index does not explain why surfaces obey the laws of reflection and refraction, so R is not the explanation of A.

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55.

The valence electron of the impurity atom that is to be added to germanium crystal so as to make it a n-type semiconductor is

Exam Year(s)

TNPSC Group 1 - 2017, TNPSC - 2017,

Answer: B

The impurity atom must have 5 valence electrons.

Germanium is in group 14 and has four valence electrons, each shared in a covalent bond with a neighbouring atom. A pentavalent dopant such as phosphorus, arsenic or antimony uses four of its five electrons in those bonds, and the fifth is only loosely held, so it is easily freed to conduct. Because the extra carriers are negative electrons, the crystal becomes an n-type semiconductor.

A trivalent impurity (3 valence electrons, such as boron or indium) leaves a hole in one bond and gives a p-type semiconductor. An atom with 4 valence electrons simply fits into the lattice like germanium itself, and 6 is not the valence of any standard dopant for germanium.

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56.

A particle executes S.H.M. The acceleration of the particle is maximum

A.at extreme position
B.at mean position
C.midway between mean and extreme position
D.acceleration is same at all position

Exam Year(s)

TNPSC Group 1 - 2017, TNPSC - 2017,

Answer: A

The acceleration is maximum at the extreme position.

In simple harmonic motion the acceleration is proportional to the displacement from the mean position and directed towards it:

\[ a = -\omega^{2} x \]

The displacement is largest, equal to the amplitude, at either extreme, so the acceleration is largest there too. At the mean position x = 0, so the acceleration is zero, while the speed is at its maximum.

So 'at mean position' confuses acceleration with velocity, the midway point gives only half the maximum value, and the acceleration is clearly not the same everywhere because it changes with x.

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57.

The velocity of sound is maximum in

A.Water
B.Air
C.Metal
D.Vacuum

Exam Year(s)

TNPSC Group 1 - 2017, TNPSC - 2017,

Answer: C

Sound travels fastest in a metal.

Sound is a mechanical wave and needs a medium. Its speed depends on how stiff the medium is compared with its density, and solids are far stiffer than liquids or gases. Typical values are about 5,000 to 6,000 m/s in steel, about 1,500 m/s in water and about 340 m/s in air.

So water is slower than metal and air slower still. In a vacuum there are no particles to carry the vibration, so sound cannot travel at all and its speed there is not a maximum but zero.

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58.

When the frequency of an electromagnetic wave and ultrasonic wave are same, then

A.their wavelengths should be same
B.wavelength of electromagnetic wave will be more
C.wavelength of ultrasonic wave will be more
D.wavelength of electromagnetic wave will be less

Exam Year(s)

TNPSC Group 1 - 2017, TNPSC - 2017,

Answer: B

The wavelength of the electromagnetic wave will be more.

For any wave, speed = frequency \(\times\) wavelength, so at the same frequency the wave that travels faster has the longer wavelength:

\[ \lambda = \frac{v}{f} \]

Electromagnetic waves travel at about \(3 \times 10^{8}\) m/s in air, while ultrasonic waves are sound and travel at only about 340 m/s. So the electromagnetic wavelength is roughly a million times longer.

The wavelengths cannot be equal because the speeds differ, and the options making the ultrasonic wavelength larger or the electromagnetic one smaller say the opposite of the result.

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59.

A convex lens of focal length 40 cm is in contact with a concave lens of focal length 25 cm. The power of the combination is

A.-1.5 D
B.-6.5 D
C.+1.5 D
D.+6.5 D

Exam Year(s)

TNPSC Group 1 - 2017, TNPSC - 2017,

Answer: A

The power of the combination is -1.5 D.

Power in dioptres is the reciprocal of the focal length in metres, positive for a convex lens and negative for a concave lens. For lenses in contact, the powers add:

\[ \begin{aligned} P &= \frac{1}{0.40} + \left(-\frac{1}{0.25}\right) \\ &= 2.5 - 4 = -1.5\ \text{D} \end{aligned} \]

+1.5 D ignores the fact that the stronger concave lens wins, and ±6.5 D comes from adding the two powers as if both had the same sign.

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60.

Which of the following has the least wavelength?

A.X-rays
B.Microwaves
C.Ultra Violet rays
D.Radio waves

Exam Year(s)

TNPSC Group 1 - 2017, TNPSC - 2017,

Answer: A

X-rays have the least wavelength among these.

In order of decreasing wavelength the electromagnetic spectrum runs: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays. Radio waves can be metres to kilometres long, microwaves millimetres to centimetres, ultraviolet about 10 to 400 nm, and X-rays roughly 0.01 to 10 nm.

So of the four options X-rays are shortest; ultraviolet is next, and microwaves and radio waves are far longer.

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