The phenomenon of diffraction limits the resolving power of optical instruments because: MCQ with Answer and Explanation

The phenomenon of diffraction limits the resolving power of optical instruments because:
A. Mirrors reflect imperfectly
B. Light bends around edges, causing image blurring
C. Lenses absorb light
D. Atmospheric turbulence distorts light
Answer: Option B
Solution (By JKSSB Mock Tests)
Diffraction causes light waves to spread when passing through apertures or around obstacles, creating Airy patterns instead of point images. This fundamental wave effect limits the minimum resolvable detail (Rayleigh criterion: θ_min ≈ 1.22λ/D). Options B, C, D are practical limitations but not the fundamental diffraction limit. Memory tip: 'Diffraction limit: smaller λ or larger aperture ⇒ better resolution'. This wave optics concept is frequently tested in competitive exams. Always distinguish fundamental limits (diffraction) from technical limitations (aberrations, turbulence) in instrument performance.

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Practice More Physics Questions

Question #1
One astronomical unit (AU) is the
A. Distance between Earth and Sun
B. Distance travelled by light in one year
C. Distance between Earth and Moon
D. Radius of Earth

Correct Answer: Option A


Explanation:
1 AU ≈ 1.5 × 10⁸ km, average Earth-Sun distance.

This question belongs to: Science Physics
Question #2
Two 60 W bulbs are connected in series across 220 V. Each bulb power becomes (approximately)
A. 30 W
B. 120 W
C. 60 W
D. 15 W

Correct Answer: Option D


Explanation:
Each bulb R = 220²/60 ≈ 807 Ω. Series total R=1614 Ω, current = 220/1614 ≈0.136 A. Power per bulb = I²R = (0.136)²×807 ≈ 15 W.

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Question #3
Two parallel wires carrying direct currents in the opposite directions will:
A. Attract each other
B. Repel each other
C. Have no effect on each other
D. Rotate perpendicular to each other

Correct Answer: Option B


Explanation:
According to Ampere's force law, parallel wires carrying currents in the SAME direction create magnetic fields that attract each other. Conversely, parallel wires carrying currents in OPPOSITE directions create magnetic fields that push against each other, causing the wires to repel. Exam tip: 'Same' Attracts, 'Opposite' Repels (reverse of charges!).

This question belongs to: Science Physics