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 7 of 34
121. A diffraction grating has 500 lines per mm. Its slit spacing or grating element will be equal to
- A. 500 mm
- B. 5 x 10^(-3) mm
- C. 2 x 10^(-6) m
- D. 21 x 10^(-3) mm
Explanation: Slit spacing d = 1 / (lines per unit length) = 1 / (500 per mm) = 2×10⁻³ mm = 2×10⁻⁶ m.
Correct answer: 2 x 10^(-6) m- A. in all directions
- B. in two mutually perpendicular directions
- C. taking place perpendicular to the direction of propagation of light
- D. no vibration at all
Explanation: Explanation: In plane-polarized light, the electric vibrations occur in a specific plane, and the vibrations are perpendicular to the…
Correct answer: in two mutually perpendicular directions- A. plane-polarized
- B. unpolarized
- C. circularly polarized
- D. elliptically polarized
Explanation: Explanation: A Polaroid is a type of polarizing filter that allows only light waves vibrating in a particular plane to pass through.
Correct answer: plane-polarized- A. radio waves
- B. ultraviolet rays
- C. X-rays
- D. ultrasonic waves
Explanation: Explanation: Radio waves are typically not polarized. Unlike light waves, which can be easily polarized using filters, radio waves do not…
Correct answer: radio waves- A. 3λ/2c
- B. 2λ/c
- C. 3λ/c
- D. 4λ/c
Explanation: Explanation: The time taken for a portion of a wavefront to reach a point 'P' when a monochromatic plane wave is diffracted at a small…
Correct answer: 2λ/c- A. Reduce the intensity of light
- B. Produce polarized light
- C. Increase the intensity of light
- D. Both (a) and (b)
Explanation: Explanation: A polarizer is an optical filter that allows light waves of a specific polarization to pass through while blocking light…
Correct answer: Both (a) and (b)- A. No interference fringes are observed
- B. No diffraction fringes are observed
- C. No fringes are observed
- D. Interference pattern is not disturbed
Explanation: Explanation: In a double-slit experiment, when one of the two slits is covered, the interference pattern is disrupted, and no interference…
Correct answer: No interference fringes are observed- A. Newton
- B. Einstein
- C. Michelson
- D. Galileo
Explanation: Explanation: Albert A. Michelson is credited with proposing the idea of defining the meter in terms of the wavelength of red cadmium…
Correct answer: Michelson- A. λ
- B. λ/3
- C. λ/6
- D. λ/4
Explanation: Explanation: In Michelson interferometer, to switch the fringe from bright to dark (or vice versa), the mirror needs to be displaced by a…
Correct answer: λ/6- A. Interference
- B. Diffraction
- C. Polarization
- D. Refraction
Explanation: Explanation: The phenomenon where the central portion of the shadow of an opaque object appears bright is due to diffraction.
Correct answer: Diffraction- A. Diffraction
- B. Polarization
- C. Interference
- D. Reflection
Explanation: Explanation: Diffraction is the phenomenon where waves bend around obstacles or spread when passing through an aperture.
Correct answer: Diffraction- A. increasing the objective focal length and decreasing the eyepiece focal length
- B. increasing the lens diameters
- C. decreasing the lens diameters
- D. inserting a correction lens between objective and eyepiece
Explanation: Reason: Increasing the objective focal length and decreasing the eyepiece focal length improves the resolving power of the telescope by…
Correct answer: increasing the objective focal length and decreasing the eyepiece focal length- A. Graham Bell
- B. Galileo
- C. Torricelli
- D. Maxwell
Explanation: Reason: The photophone, an early device for transmitting sound on a beam of light, was invented by Alexander Graham Bell.
Correct answer: Graham Bell- A. lambda:
- B. 1/lambda:
- C. lambda^2:
- D. 1/lambda^2
Explanation: Reason: The resolving power of a microscope is inversely proportional to the square of the wavelength of light used.
Correct answer: 1/lambda^2- A. 1.3 gm:
- B. 1.3 nm
- C. 13 gm:
- D. 13 nm:
Explanation: Reason: Typical fiber optic communication systems use light with wavelengths around 1.3 nm or 1.55 nm.
Correct answer: 1.3 nm- A. A is P/2:
- B. A is 2P
- C. C is P:
- D. B is P/2:
Explanation: Explanation: Cutting a lens into two equal halves reduces the power by half. Therefore, the power of part A is P/2.
Correct answer: A is 2P- A. Intensity becomes double:
- B. Image will not be formed:
- C. Intensity will remain the same
- D. Intensity will become half:
Explanation: Explanation: Covering a lens with wax affects the transmission of light, but it does not change the intensity of light.
Correct answer: Intensity will remain the same- A. 2f
- B. 2.5f:
- C. 3f:
- D. 4f:
Explanation: Explanation: For a convex lens, the minimum distance between an object and its real image occurs when the object is placed at twice the…
Correct answer: 2f- A. 100 cm, -4 cm:
- B. -80 cm, -6 cm:
- C. 90 cm, -6 cm
- D. 90 cm, 6 cm:
Explanation: Explanation: The focal length of the telescope objective lens is positive, and that of the eyepiece is negative.
Correct answer: 90 cm, -6 cm- A. Increases with an increase in focal length:
- B. Increases with a decrease in focal length
- C. No effect with decrease or increase in focal length:
- D. Least distance of distinct vision:
Explanation: Explanation: The magnifying power of a simple microscope increases with a decrease in focal length.
Correct answer: Increases with a decrease in focal length