Free Optics MCQs with Answers
665 Optics MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Light is studied through reflection, refraction, dispersion, interference, diffraction and polarization, linking ray behavior with its wave nature. Questions may involve mirrors, lenses, optical instruments, refractive index and image formation, while geometrical optics deals with rays and wave optics explains effects such as interference and diffraction.
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665 questions · page 3 of 34
41. Errors in the transmission of power through optic fiber can be minimized by using a______________?
- A. Multimode index fiber
- B. Graded index fiber
- C. Single mode step index fiber
- D. Copper wire
Explanation: A graded-index fibre has a core whose refractive index gradually decreases from the centre outward, causing different modes to travel with…
Correct answer: Graded index fiber- A. fo+fe
- B. fo/fe
- C. fe/fo
- D. (1+fo/fe)L/fo
Explanation: For an astronomical telescope in normal adjustment, the objective forms an image at its focal plane and the eyepiece magnifies it, giving…
Correct answer: fo/fe- A. Diodes
- B. Repeaters
- C. Laser
- D. Transformer
Explanation: Repeaters receive weakened optical signals, amplify or regenerate them, and send fresh signals into the next section of fibre.
Correct answer: Repeaters- A. 42°
- B. 47°
- C. 52°
- D. 50°
Explanation: For ordinary glass surrounded by air, the critical angle is approximately 42°, obtained from sin C = 1/n, with glass refractive index…
Correct answer: 42°- A. center of curvature
- B. focus
- C. optical center
- D. aperture
Explanation: The focus is the point where rays parallel to the principal axis actually meet after a converging lens or appear to originate after a…
Correct answer: focus- A. 2 f
- B. 2.5 f
- C. 3f
- D. 4f
Explanation: For a convex lens, the separation between a real object and its real image is minimum when the object and image are both at 2f.
Correct answer: 4f- A. between principal focus and center of curvature
- B. beyond 2 f
- C. at the principal focus
- D. between principal focus and optical center
Explanation: A convex lens forms a virtual, erect and magnified image when the object is placed between the principal focus and the optical centre.
Correct answer: between principal focus and optical center48. Image of an object 5 mm high is only 1 cm high. Magnification produced by lens is__________________?
- A. 0.5
- B. 0.2
- C. 1
- D. 2
Explanation: Magnification is image height divided by object height: m = 1 cm / 5 mm = 10 mm / 5 mm = 2.
Correct answer: 2- A. increases with increase in age
- B. decreases with increase in age
- C. neither increases nor decreases
- D. becomes infinite after 60 years
Explanation: The least distance of distinct vision generally increases with age because the eye's lens loses elasticity and the ciliary muscles become…
Correct answer: increases with increase in age- A. zero
- B. focus
- C. 2 f
- D. f/2
Explanation: For two thin lenses in contact, their powers add: 1/F = 1/f + 1/f = 2/f. Hence F = f/2, where F and f have the same unit of length.
Correct answer: f/2- A. fo + fe
- B. fo - fe
- C. fo / fe
- D. fe / fo
Explanation: In normal adjustment, the intermediate image formed by the objective lies at the focal point of the eyepiece, so the final image is at…
Correct answer: fo + fe- A. real and inverted
- B. real and erect
- C. virtual and erect
- D. virtual and inverted
Explanation: The objective of a compound microscope first forms a real, inverted intermediate image.
Correct answer: virtual and inverted- A. same
- B. different
- C. zero
- D. different with refractive index of core higher than cladding
Explanation: A step-index fibre has a sudden change in refractive index at the core-cladding boundary, so the core and cladding have different…
Correct answer: different with refractive index of core higher than cladding- A. chromatic aberration
- B. spherical aberration
- C. both spherical and chromatic
- D. distortion
Explanation: Spherical aberration occurs because rays striking different zones of a large-aperture spherical lens are brought to different focal…
Correct answer: spherical aberration- A. 15 cm
- B. 25 cm
- C. 30 cm
- D. 40 cm
Explanation: For a normal eye, the least distance of distinct vision is 25 cm, called the near point.
Correct answer: 25 cm- A. increase with increase in focal length
- B. increase with decrease in focal length
- C. no effect with decrease or increase with focal length
- D. list distance of distinct vision
Explanation: The magnifying power of a simple microscope is proportional to 1/f, so reducing the focal length increases magnification.
Correct answer: increase with decrease in focal length- A. real and erect
- B. virtual and erect
- C. real and inverted
- D. virtual
Explanation: When an object is placed beyond 2f of a converging lens, the refracted rays meet on the opposite side between f and 2f.
Correct answer: real and inverted- A. real
- B. virtual
- C. positive
- D. negative
Explanation: A concave lens causes parallel rays to diverge, so its focal point is virtual and its focal length is negative.
Correct answer: negative- A. meter
- B. watt
- C. diopter
- D. horsepower
Explanation: The power of a lens is P = 1/f, where f is in metres, so its unit is m^-1, called the dioptre.
Correct answer: diopter- A. Electron microscope
- B. Scanning electron microscope
- C. Magnetic imaging
- D. None of the aboveElectron Microscopes
Explanation: A scanning electron microscope scans a focused electron beam over a specimen and detects secondary electrons from its surface, producing a…
Correct answer: Scanning electron microscope