Free Optics MCQs with Answers

• A. Water
• B. Glass
• C. Air
• D. Diamond

Explanation: The speed of light decreases as the refractive index increases. Air has the lowest refractive index (~1.0003), so light travels fastest in…

• A. Reflection
• B. Refraction
• C. Diffraction
• D. Polarization

Explanation: Longitudinal waves (compressions along propagation) can reflect, refract, and diffract, but cannot be polarised because their oscillations…

• A. An elliptical wave front
• B. A cylindrical wave front
• C. A plane wave front
• D. A rectangular wave front

Explanation: Far from a point source (large radius of curvature), the spherical wavefront locally approximates a plane wavefront, so waves appear…

• A. Iconography
• B. Holography
• C. Logography
• D. Photography

Explanation: Laser beams are used to create three-dimensional images (holograms) through the process of holography, which records and reconstructs…

• A. d sin θ = (m + ½ ) λ
• B. d sin θ = m λ
• C. d sin θ = (m - ½ ) λ
• D. 2d sin θ = m λ

Explanation: Bright fringes occur when path difference equals an integer multiple of λ: d sinθ = mλ for m = 0,1,2,...; half‑integer multiples give dark…

• A. Integral multiple of λ/2
• B. Integral multiple of λ
• C. Odd integral multiple of λ/2
• D. Even integral multiple of λ/2

Explanation: Destructive interference occurs when the path difference = (2m+1)λ/2 (odd half‑wavelengths), causing waves to be out of phase by π radians…

• A. Dispersion of light
• B. Diffraction of light
• C. Scattering of light
• D. Interference of light

Explanation: Varying film thickness causes wavelength‑dependent constructive/destructive interference of reflected light, producing iridescent colours.

• A. Bright fringes are wider than dark fringes
• B. Dark fringes are wider than bright fringes
• C. Both dark and bright fringes are of equal width
• D. Central fringes are brighter than the outer fringes

Explanation: For ideal two-slit interference with uniform illumination, the bright and dark fringes alternate with equal angular spacing; bright and…

• A. Polarization of light
• B. Different elements present in the oil
• C. Interference of light
• D. The transmission of light

Explanation: Reflections from top and bottom surfaces of the oil film interfere; constructive interference for certain wavelengths yields colourful…

• A. Refraction
• B. Reflection
• C. Diffraction
• D. Dispersion

Explanation: Refraction is the change in direction of propagation when wave speed changes across a boundary, described by Snell's law n sinθ1 = n sinθ2.

• A. Diffraction
• B. Reflection
• C. Interference
• D. Polarization

Explanation: Thin-film colours result from wavelength-dependent interference between rays reflected from different film surfaces; thickness and angle…

• A. Diffraction of light
• B. Interference of light
• C. Polarization of light
• D. Reflection of light

Explanation: Newton's rings arise from interference between light reflected from the convex lens underside and the flat glass plate, producing…

• A. 10 Å
• B. 100 Å
• C. 1 Å
• D. 1000 Å

Explanation: X‑ray wavelengths are on the order of 1 Å (angstrom ≈ 10⁻¹⁰ m), comparable to interatomic spacings, enabling crystallographic diffraction.

• A. Temperature
• B. Wavelength of light
• C. Nature of the medium
• D. All of these

Explanation: Refractive index changes with temperature, wavelength (dispersion), and the material's optical density.

• A. d = λ /2
• B. d = 3 λ /2
• C. d = 5 λ /2
• D. d = m λ

Explanation: Constructive interference occurs when the path difference equals an integer multiple of the wavelength: d = m λ (m = 0,1,2,...), producing…

• A. Real and inverted images only
• B. Virtual and erect images only
• C. Both real and virtual images
• D. Neither real nor virtual images

Explanation: A convex lens can form real images (when the object is beyond the focal point) and virtual images (when the object is between the focal…

• A. Convex lens
• B. Concave lens
• C. Cylindrical lens
• D. Bifocal lens

Explanation: Myopia is corrected using a concave (diverging) lens, which spreads light rays so they focus correctly on the retina.

• A. Accelerated bodies
• B. Heating a conductor
• C. Charges at rest or in uniform motion
• D. Accelerated charges

Explanation: Time‑varying (accelerated) charges produce varying electric and magnetic fields that radiate as electromagnetic waves; uniform motion or…

• A. Greater than that of red color
• B. Less than that of red color
• C. The same as that of red color
• D. None of these

Explanation: Violet light has a higher frequency (shorter wavelength) than red; since E = h f, the photon energy for violet > red.

• A. I and II are correct
• B. II and III are correct
• C. III and IV are correct
• D. I and IV are correct

Explanation: The photoelectric effect and the Compton effect provide clear evidence for quantised photons and particle-like interactions of light with…