Quiz — BAS101

Q1. Which experiment provided a key null result motivating special relativity?

A. Rutherford scattering B. Michelson–Morley experiment C. Davisson–Germer experiment D. Millikan oil-drop experiment

Q2. Einstein's second postulate of special relativity states that:

A. Mass is conserved in all frames B. The speed of light in vacuum is the same for all inertial observers C. Time is absolute D. Energy is not conserved at relativistic speeds

Q3. The Lorentz factor γ is defined as:

A. 1/(1 - v/c) B. √(1 - v²/c²) C. 1/√(1 - v²/c²) D. v²/c²

Q4. According to length contraction, a moving rod appears:

A. Longer than its rest length B. Shorter than its rest length C. Unchanged in length D. Curved

Q5. Time dilation implies that a clock moving relative to an observer:

A. Runs faster B. Runs slower C. Stops completely D. Is unaffected

Q6. The mass–energy equivalence relation is:

A. E = mc B. E = mc² C. E = m/c² D. E = m²c

Q7. A reference frame in which Newton's first law holds is called:

A. Non-inertial frame B. Inertial frame C. Rotating frame D. Rest frame

Q8. The relativistic energy–momentum relation is:

A. E² = (pc)² + (m₀c²)² B. E = pc² C. E² = pc + m₀c D. E = p²c² - m₀c²

Q9. The Galilean transformation fails to explain:

A. Motion of slow objects B. Constancy of the speed of light C. Newton's laws in inertial frames D. Conservation of momentum

Q10. As v → c, the relativistic mass of a particle:

A. Approaches zero B. Remains constant C. Tends to infinity D. Becomes negative

Q11. Sustained interference between two sources requires:

A. Different frequencies B. A constant phase relationship (coherence) C. Very large source separation D. White light only

Q12. In Fresnel's biprism experiment, the two coherent sources are produced by:

A. Two independent lamps B. Refraction through a thin-angle prism C. Diffraction at an aperture D. Reflection from two mirrors

Q13. Fringe width in a biprism experiment is given by β =

A. λD/d B. λd/D C. Dd/λ D. λ/D

Q14. In thin film interference by reflection, an additional path difference of λ/2 arises when light:

A. Passes from denser to rarer medium B. Reflects from rarer to denser medium C. Travels in vacuum D. Is completely absorbed

Q15. The condition for a bright fringe in a wedge-shaped thin air film (reflected system) is:

A. 2μt cosr = nλ B. 2μt cosr = (n + ½)λ C. μt = nλ/2 D. t = nλ

Q16. In Newton's rings experiment, the radius of the nth dark ring (reflected light) is proportional to:

A. n² B. √n C. n D. 1/n

Q17. Newton's rings are used experimentally to determine:

A. The speed of light B. The wavelength of light or radius of curvature of a lens C. The mass of an electron D. The refractive index of air only

Q18. A wedge-shaped film produces fringes that are:

A. Circular B. Equally spaced and straight C. Randomly distributed D. Elliptical

Q19. The centre of the Newton's rings pattern (by reflection) is:

A. Bright B. Dark C. Coloured D. Absent

Q20. Interference in thin films is best observed with:

A. Very thick films only B. Films of thickness comparable to the wavelength of light C. Opaque films D. Films thicker than 1 cm

Q21. In single-slit diffraction, the condition for minima is:

A. a sinθ = nλ B. a sinθ = (n+½)λ C. a cosθ = nλ D. a tanθ = nλ

Q22. The central maximum in single-slit diffraction is:

A. Same width as subsidiary maxima B. Half the width of subsidiary maxima C. Twice the width of subsidiary maxima D. Absent

Q23. In a diffraction grating, the grating element refers to:

A. The width of a single slit B. The sum of slit width and opaque spacing (a+b) C. The number of slits per cm D. The order of the spectrum

Q24. The principal maxima condition for a diffraction grating is:

A. (a+b) sinθ = nλ B. (a+b) cosθ = nλ C. a sinθ = (a+b)λ D. nλ = a - b

Q25. The resolving power of a grating is given by R = λ/dλ =

A. N/n B. nN C. n/N D. N + n

Q26. Rayleigh's criterion for just-resolved spectral lines states that:

A. The two maxima must coincide exactly B. The principal maximum of one falls on the first minimum of the other C. The lines must be separated by more than one grating order D. Resolution is independent of wavelength

Q27. As the number of illuminated slits N increases, the diffraction grating's principal maxima become:

A. Broader and dimmer B. Sharper and more intense C. Unchanged D. Completely absent

Q28. Diffraction differs fundamentally from interference in that diffraction involves:

A. Only two coherent sources B. Superposition of wavelets from the same wavefront (secondary wavelets) C. No superposition of waves D. Only reflection

Q29. A diffraction grating is generally preferred over a prism for spectroscopy because it offers:

A. Lower resolving power B. Simple construction only C. Much higher resolving power and better wavelength separation D. No dependence on wavelength

Q30. The intensity pattern in N-slit diffraction shows subsidiary maxima whose number is:

A. Independent of N B. N - 2 between successive principal maxima C. Always exactly 2 D. Always zero

Q31. Double refraction (birefringence) occurs in crystals such as:

A. Glass B. Calcite C. Water D. Air

Q32. In a Nicol prism, the ordinary ray is eliminated by:

A. Absorption in the crystal itself B. Total internal reflection at the Canada balsam layer C. Diffraction at the crystal edge D. Refraction into a second crystal

Q33. A quarter-wave plate introduces a path difference of:

A. λ/2 B. λ C. λ/4 D. 2λ

Q34. A half-wave plate introduces a phase difference of:

A. 90° B. 180° C. 360° D. 45°

Q35. Plane polarized light passed through a quarter-wave plate at 45° to the optic axis becomes:

A. Plane polarized B. Circularly polarized C. Unpolarized D. Extinguished completely

Q36. Optical activity refers to the property of certain substances to:

A. Absorb all incident light B. Rotate the plane of polarization of light C. Emit light spontaneously D. Reflect light totally

Q37. Fresnel explained optical activity using the idea that plane polarized light is equivalent to:

A. Two waves of different wavelength B. Two counter-rotating circularly polarized components of different velocity C. A single unpolarized wave D. Two waves of different intensity

Q38. A polarimeter is used to measure:

A. Refractive index of a liquid B. Specific rotation of an optically active substance C. Wavelength of X-rays D. Focal length of a lens

Q39. The ordinary ray in a doubly refracting crystal obeys:

A. No physical law B. Snell's law C. Bragg's law D. Malus' law only

Q40. Malus' law relates the intensity of light transmitted through a polarizer to:

A. The wavelength of light B. The square of the cosine of the angle between polarizer axes C. The refractive index of air D. The speed of light

Q41. Stimulated emission produces a photon that is:

A. Random in phase and direction relative to the incident photon B. Identical in phase, frequency and direction to the incident photon C. Always of higher energy D. Always absorbed immediately

Q42. Population inversion in a laser medium means:

A. More atoms in the ground state than excited state B. More atoms in the excited state than the lower state C. Equal population in all states D. No atoms in the excited state

Q43. The Einstein coefficients A and B relate to:

A. Spontaneous emission, stimulated emission and absorption probabilities B. Only reflection of light C. The speed of light in a medium D. Electron spin only

Q44. The Ruby laser operates as a:

A. Four-level, continuous wave laser B. Three-level, pulsed solid-state laser C. Gas laser only D. Semiconductor laser

Q45. The He-Ne laser emits its principal output at a wavelength of approximately:

A. 532 nm B. 694.3 nm C. 632.8 nm D. 1064 nm

Q46. Holography records both the ___ of light scattered from an object.

A. Amplitude and phase B. Colour and temperature C. Mass and charge D. Speed and direction only

Q47. Reconstructing a hologram requires illuminating it with:

A. White light only, from any direction B. A beam similar to the original reference beam C. Ultraviolet light only D. No light at all

Q48. Optical fibres guide light through the core mainly due to:

A. Diffraction at the core-cladding boundary B. Total internal reflection at the core–cladding interface C. Absorption by the cladding D. Polarization effects only

Q49. The numerical aperture (NA) of an optical fibre is given by:

A. n₁ + n₂ B. √(n₁² − n₂²) C. n₁ / n₂ D. n₁ × n₂

Q50. Attenuation in optical fibres arises mainly due to:

A. Only mechanical vibration B. Absorption, scattering and bending losses C. Only the light source used D. Gravity

BAS10150-Question MCQ Quiz