Physics MCQs

Question #201

A radioactive sample has a half-life of 5 years. What fraction of the original active nuclei will remain undecayed after 15 years?

A. 1/2

B. 1/3

C. 1/15

D. 1/8

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option D

Explanation:
The number of half-lives (n) that have passed is total time / half-life = 15 / 5 = 3 half-lives. The fraction of the sample remaining undecayed is given strictly by the formula (1/2)^n. Therefore, the fraction remaining is (1/2)^3 = 1/2 * 1/2 * 1/2 = 1/8.

This question belongs to: Science Physics

Question #202

Share Report

Which combination of logic gates is universally known as a 'Universal Gate' because it can be used to construct any other basic logic gate (AND, OR, NOT)?

A. NOT and AND

B. AND and OR

C. NAND and NOR

D. XOR and XNOR

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option C

Explanation:
NAND (NOT-AND) and NOR (NOT-OR) gates are called Universal Gates in digital electronics. By cleverly combining multiple NAND gates (or multiple NOR gates) together, one can perfectly replicate the logical function of any basic gate (NOT, AND, OR) without needing the actual basic gates themselves.

This question belongs to: Science Physics

Question #203

Share Report

Which scientific instrument is used specifically for measuring very high temperatures, such as the surface temperature of the Sun or inside a furnace, from a distance?

A. Bolometer

B. Pyrometer

C. Cryometer

D. Calorimeter

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option B

Explanation:
A pyrometer is a non-contact thermometer used to measure high temperatures. It operates on the principle of thermal radiation (Stefan-Boltzmann law or Wien's law), measuring the intensity or spectrum of electromagnetic radiation emitted by the extremely hot object. A cryometer measures very low temperatures, and a calorimeter measures heat capacity.

This question belongs to: Science Physics

Question #204

Share Report

The fundamental principle utilized in an optical endoscope, which allows doctors to examine the inside of the human body, is:

A. Scattering of light

B. Total internal reflection of light

C. Diffraction of light

D. Polarization of light

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option B

Explanation:
Endoscopes consist of bundles of flexible optical fibers. Light introduced at one end is trapped inside the fiber core because it repeatedly strikes the boundary at an angle greater than the critical angle. This Total Internal Reflection allows light and visual images to be transmitted through complex, curving paths inside the body.

This question belongs to: Science Physics

Question #205

Share Report

A typical Cathode Ray Oscilloscope (CRO) is fundamentally designed to visually display and analyze which physical quantity with respect to time?

A. Temperature

B. Magnetic Field

C. Pressure

D. Voltage

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option D

Explanation:
A CRO uses an electron beam sweeping across a phosphorescent screen to create a visible graph. It is fundamentally a voltage-measuring instrument. The vertical deflection is directly proportional to the applied voltage, and the horizontal deflection is controlled by a time-base generator, allowing it to display voltage waveforms over time.

This question belongs to: Science Physics

Question #206

Share Report

The essential condition required for Laser action to occur in a medium is known as:

A. Population inversion

B. Spontaneous emission

C. Photoelectric emission

D. Thermal equilibrium

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
Laser (Light Amplification by Stimulated Emission of Radiation) requires that more atoms exist in a high-energy excited state than in a lower energy state. This unnatural, non-equilibrium condition is called 'population inversion'. Without it, absorption would dominate over stimulated emission, and the beam would not be amplified.

This question belongs to: Science Physics

Question #207

Share Report

The Chandrasekhar Limit is a fundamental concept in astrophysics that determines the ultimate fate of a star. It is specifically defined as the maximum mass of a:

A. White Dwarf

B. Black Hole

C. Neutron Star

D. Red Giant

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
Subrahmanyan Chandrasekhar calculated that a White Dwarf star cannot support itself against gravitational collapse if its mass exceeds approximately 1.44 times the mass of our Sun. This is the Chandrasekhar limit. Stars above this mass limit will eventually collapse further into a dense neutron star or a black hole.

This question belongs to: Science Physics

Question #208

Share Report

Enrico Fermi is most famously recognized for his pioneering achievement in building the world's first:

A. Particle Accelerator (Cyclotron)

B. X-ray machine

C. Atomic Bomb

D. Nuclear Reactor

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option D

Explanation:
Enrico Fermi led the team that constructed 'Chicago Pile-1', which achieved the world's first artificial, self-sustaining nuclear chain reaction on December 2, 1942. This was the first nuclear reactor. While he worked on the Manhattan Project (atomic bomb), his crowning individual distinction is creating the first controlled reactor.

This question belongs to: Science Physics

Question #209

Share Report

If the earth suddenly shrinks to half its present radius without any change in its mass, the duration of a day on earth will become:

A. 48 hours

B. 12 hours

C. 6 hours

D. 24 hours

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option C

Explanation:
By conservation of angular momentum: I1w1 = I2w2. Moment of inertia of a solid sphere is 2/5 MR^2. So, (R1^2) * (2pi/T1) = (R2^2) * (2pi/T2). If radius halves, R2 = R1/2. R1^2 / T1 = (R1/2)^2 / T2. T2 = T1 / 4. A day is 24 hours, so 24/4 = exactly 6 hours.

This question belongs to: Science Physics

Question #210

Share Report

Which one of the following graphs accurately represents the variation of magnetic field (B) with distance (r) from the exact center of a solid, current-carrying cylindrical wire of radius R?

A. B is inversely proportional to r everywhere.

B. B is zero everywhere inside, and inversely proportional to r outside.

C. B is constant inside, and directly proportional to r outside.

D. B is directly proportional to r inside, and inversely proportional to r outside.

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option D

Explanation:
By Ampere's Circuital Law, for a solid wire carrying uniform current, the magnetic field inside (r < R) is B = (mu_0 * I * r) / (2piR^2), meaning B ∝ r (straight line). Outside the wire (r > R), B = (mu_0 * I) / (2pi*r), meaning B ∝ 1/r (rectangular hyperbola). Thus, it increases linearly then decays.

This question belongs to: Science Physics

Question #211

Share Report

A tuning fork A produces 5 beats/second with tuning fork B of frequency 256 Hz. If a little wax is applied to fork A, the beat frequency becomes 2 beats/second. The original frequency of fork A was:

A. 251 Hz

B. 254 Hz

C. 258 Hz

D. 261 Hz

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option D

Explanation:
The beat frequency is |fA - fB|. So fA is either 256+5=261 Hz or 256-5=251 Hz. Adding wax increases mass, which strictly decreases frequency. If fA was 261, decreasing it brings it closer to 256, reducing beats to 2 (e.g., 258-256=2). If it was 251, decreasing it would increase the beats (e.g., |248-256|=8). Thus, it was 261 Hz.

This question belongs to: Science Physics

Question #212

Share Report

An electron and a proton are accelerated through the exact same potential difference. Which particle will acquire a greater kinetic energy?

A. The proton

B. The electron

C. Both will acquire the exact same kinetic energy

D. Depends on their initial velocities

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option C

Explanation:
The work done by the electric field on a charged particle is completely converted into kinetic energy. Work = q * V, where q is the magnitude of the charge and V is the potential difference. Since both an electron and a proton have the exact same magnitude of charge (e = 1.6 x 10^-19 C), they acquire identical kinetic energy (eV).

This question belongs to: Science Physics

Question #213

Share Report

Which of the following is a fundamental unit in the SI system?

A. Pascal

B. Candela

C. Newton

D. Joule

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option B

Explanation:
The seven fundamental SI units are: metre (m), kilogram (kg), second (s), ampere (A), kelvin (K), mole (mol), and candela (cd). Candela is the unit of luminous intensity. Newton, joule, and pascal are derived units. Newton = kg·m/s², joule = kg·m²/s², pascal = kg/(m·s²). Hence, candela is a fundamental unit. Exam tip: Remember the acronym ‘MKS A K M C’ for the seven base units.

This question belongs to: Science Physics

Question #214

Share Report

The dimension of Planck's constant is same as that of

A. Energy

B. Force

C. Linear momentum

D. Angular momentum

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option D

Explanation:
Planck's constant h = E/ν, so its dimensions are [Energy]/[Frequency] = [ML²T⁻²]/[T⁻¹] = [ML²T⁻¹]. Angular momentum = mvr = M·LT⁻¹·L = [ML²T⁻¹]. Energy = [ML²T⁻²], linear momentum = [MLT⁻¹], force = [MLT⁻²]. Thus, Planck's constant and angular momentum share dimensions. This is a key dimensional match in quantum mechanics.

This question belongs to: Science Physics

Question #215

Share Report

The number of significant figures in 0.0034060 is

A. 4

B. 7

C. 5

D. 6

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option C

Explanation:
Leading zeros (before first non-zero digit) are not significant. So 0.0034060: the first non-zero is 3, then 4,0,6 are significant, and the trailing zero after decimal is significant. Thus significant digits are 3,4,0,6,0 — 5 digits. Note: The last zero indicates precision. Answer is 5.

This question belongs to: Science Physics

Question #216

Share Report

If the speed of light is taken as 3 × 10⁸ m/s, its value in scientific notation with three significant figures is:

A. 3.00 × 10⁸ m/s

B. 3.0 × 10⁸ m/s

C. 300000000 m/s

D. 3 × 10⁸ m/s

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
Three significant figures require the number to be written with three meaningful digits. 3.00 × 10⁸ m/s has three significant figures (3,0,0). 3 × 10⁸ has one significant figure; 3.0 × 10⁸ has two; 300000000 has ambiguous significance. Standard scientific notation: 3.00 × 10⁸ m/s. This is important in precision measurements.

This question belongs to: Science Physics

Question #217

Share Report

Which of the following prefix represents 10⁻¹⁵?

A. Femto

B. Atto

C. Pico

D. Nano

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
Femto (f) = 10⁻¹⁵. Pico (p) = 10⁻¹², nano (n) = 10⁻⁹, atto (a) = 10⁻¹⁸. The prefix chain: milli 10⁻³, micro 10⁻⁶, nano 10⁻⁹, pico 10⁻¹², femto 10⁻¹⁵, atto 10⁻¹⁸. Mnemonic: Femto is 'fifteen'.

This question belongs to: Science Physics

Question #218

Share Report

The dimensional formula of pressure is

A. [M⁰L⁻¹T⁻²]

B. [MLT⁻²]

C. [ML⁻¹T⁻²]

D. [ML²T⁻²]

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option C

Explanation:
Pressure = Force/Area. Force = mass × acceleration, dimensions [MLT⁻²]. Area = L². So pressure = [MLT⁻²]/[L²] = [ML⁻¹T⁻²]. This is also the dimension of stress. Common exam trap: confuse with energy density which is also [ML⁻¹T⁻²].

This question belongs to: Science Physics

Question #219

Share Report

A ball is thrown vertically upward with speed 20 m/s. The maximum height reached (g = 10 m/s²) is

A. 10 m

B. 40 m

C. 20 m

D. 200 m

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option C

Explanation:
Using v² = u² - 2gH, at maximum height v = 0. So 0 = 20² - 2×10×H => 400 = 20H => H = 20 m. Alternative formula: H = u²/(2g) = 400/20 = 20 m. Remember to use consistent units. For quick calculation, u²/(2g) is handy.

This question belongs to: Science Physics

Question #220

Share Report

The slope of a displacement-time graph for uniform motion is

A. Velocity

B. Displacement

C. Zero

D. Acceleration

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
Displacement-time graph slope = Δx/Δt = average velocity. For uniform motion, velocity constant, graph is a straight line, slope equals velocity. Acceleration would be slope of velocity-time graph. Thus, slope represents velocity. Exam trick: slope of x-t graph gives instantaneous velocity.

This question belongs to: Science Physics

Practice Questions

More Science Topics