Free Dawn of Modern Physics MCQs with Answers

• A. Polymerization
• B. Cleavage
• C. Microstructure
• D. Dislocation

Explanation: Microstructure, including grains, grain boundaries, phases and defects, controls bulk behaviour such as strength and mode of fracture.

• A. A party filled valence band and totally empty conduction band
• B. A completely filled valence band a totally empty conduction band and a very wide forbidden band
• C. A completely filled valence band a partially filled conduction band and a narrow forbidden band
• D. A partly filled valence band a totally empty conduction band and a wide forbidden band

Explanation: A semiconductor has a filled valence band and a small forbidden energy gap, so some electrons can reach the conduction band at ordinary…

• A. Decreases
• B. Increases
• C. Remains same
• D. First increases then decreases

Explanation: Heating an intrinsic semiconductor supplies energy across its small band gap, creating more electron-hole pairs and increasing the number…

• A. Semi conductor
• B. Conductor
• C. Metals
• D. Non metals

Explanation: Non-metals that are electrical insulators generally have the largest forbidden energy gaps, while metals have overlapping or zero…

• A. Electrical insulators alone
• B. Electrical conductors alone
• C. Electrical semi conductors alone
• D. All of the above

Explanation: Band theory explains all three classes: conductors have overlapping or partly filled bands, semiconductors have a small forbidden gap, and…

• A. Kelvin
• B. Newton
• C. Aristotle
• D. Faraday

Explanation: Aristotle wrote Physics, an ancient work discussing nature, motion and change, and it is commonly regarded in general-knowledge questions…

• A. 10 micrometer
• B. 100 micrometer
• C. 1 micrometer
• D. 2 micrometer

Explanation: A photon's speed is 3x108 m/s (as it is the fundamental particle of light, and this is light's speed), and since the velocity of a wave is…

• A. 5 x 10^14 Hz
• B. 6 x 10^14 Hz
• C. 7 x 10^14 Hz
• D. 9 x 10^14 H

Explanation: The relation between frequency and wavelength is given by v = fλ. Given that, Speed of light = v = 3 x 108 m/s.Wavelength λ = 500…

• A. Equal
• B. Higher
• C. Lesser
• D. Much higher

Explanation: Laser light is basically just light. Laser light is coherent, that means it has waves of equal frequency and in phase, but other than that…

• A. Spontaneous
• B. Stimulated
• C. Both Options A and B are correct
• D. None of these options are correct

Explanation: Laser light is a type of stimulated emission where one atom is stimulated which further stimulates other atoms to release electromagnetic…

• A. Electromagnetic radiations of high mass number
• B. Electromagnetic radiations of very high frequency
• C. Electromagnetic radiations of high wavelength
• D. Electromagnetic radiations of low energy

Explanation: X-rays are electromagnetic radiations of extremely short wavelengths and high frequency, which is why option B is correct.Option C is…

• A. Interference
• B. Polarization
• C. Diffraction
• D. None of these

Explanation: In the Davisson-Germer experiment, a beam of electrons is fired at a crystal of nickel.

• A. Red
• B. Blue
• C. Black
• D. Orange

Explanation: Black is definitely an ideal absorber but we cannot say it has highest temperature.

• A. Visible light
• B. X rays
• C. Radio waves
• D. Infrared waves

Explanation: X-rays are commonly produced by accelerating (or decelerating) charged particles; examples include a beam of electrons in a synchrotron…

• A. 0.71 x 10^-29 m
• B. 1.66 x 10^29 m
• C. 1.66 x 10^-29 m
• D. 3.77 x 10^-29 m
• E. 5.71 x 10^-29 m

Explanation: The correct de Broglie wavelength is calculated using the formula λ = h/(mv).

• A. Pair production
• B. Compton effect
• C. Photoelectric effect
• D. Both Options A and B are correct

Explanation: Option A) The pair production process occurs when a high-energy photon interacts with the electromagnetic field of a nucleus, resulting in…

• A. He-Ne laser
• B. White
• C. Yellow
• D. All are equal

Explanation: All waves in the electromagnetic spectrum travel at a speed of 3 × 108 m/s.Hence, D is the correct option.

• A. Visible light
• B. X rays
• C. Radio waves
• D. Infrared

Explanation: The correct answer is X-rays. Electrons, when moving at high speeds, such as in a hydrogen atom or in a particle accelerator, have…

• A. Half the energy of a photon in beam B
• B. One-fourth the energy of a photon in beam B
• C. Equal to the energy of a photon in beam B
• D. Twice the energy of a photon in beam B

Explanation: Since energy is inversely proportional to wavelength, doubling the wavelength cuts the energy in half.

• A. Long wavelength
• B. Short wavelength
• C. Low frequency
• D. Circular motion

Explanation: The maximum kinetic energy of an electron is given by E = ℎ 𝑓 − 𝑊, m an x where ℎ is the Planck constant, 𝑓 is the frequency of the…