Chapter-10 Wave Optics — Online MCQ Test
PHYSICS · CLASS 12 SECOND PUC · Karnataka State Board
Practice Chapter-10 Wave Optics with a free chapter-wise online MCQ test.
This chapter covers: Huygens principle - wavefront - interference - Young's double slit experiment - diffraction.
AI-generated questions from basic to board-exam level, with instant results and explanations.
Chapter-10 Wave Optics — Important Questions & Answers
According to Huygens' principle, what is a wavefront?
- A. A surface joining all points that vibrate in the same phase at a given instant
- B. The envelope of all secondary wavelets at a given time
- C. Both A and B
- D. The path traced by a single particle of the medium
Answer: C. Both A and B
Huygens' principle defines a wavefront as a surface of constant phase, and it can also be understood as the envelope of all secondary wavelets generated from previous wavefront positions.
Huygens' principle defines a wavefront as a surface of constant phase, and it can also be understood as the envelope of all secondary wavelets generated from previous wavefront positions.
What type of wavefront is produced by a point source?
- A. Plane wavefront
- B. Spherical wavefront
- C. Cylindrical wavefront
- D. Elliptical wavefront
Answer: B. Spherical wavefront
A point source emits light equally in all directions, creating wavefronts that are spherical surfaces centered at the source.
A point source emits light equally in all directions, creating wavefronts that are spherical surfaces centered at the source.
When red light and blue light are used in Young's double slit experiment, which light produces wider fringes?
- A. Red light (larger wavelength)
- B. Blue light (smaller wavelength)
- C. Both produce equally wide fringes
- D. It depends on the slit separation
Answer: A. Red light (larger wavelength)
Fringe width β = λD/d increases with wavelength. Red light has larger wavelength than blue light, so it produces wider fringes.
Fringe width β = λD/d increases with wavelength. Red light has larger wavelength than blue light, so it produces wider fringes.
Which statement about the fringe visibility in Young's double slit experiment is correct?
- A. It depends only on the wavelength
- B. It is highest when the two slits have equal intensity
- C. It decreases with increasing slit width
- D. It is independent of light intensity
Answer: B. It is highest when the two slits have equal intensity
Fringe visibility is defined as (I_max - I_min)/(I_max + I_min) and is maximum (= 1) when the two slits have equal intensity; unequal intensities reduce visibility.
Fringe visibility is defined as (I_max - I_min)/(I_max + I_min) and is maximum (= 1) when the two slits have equal intensity; unequal intensities reduce visibility.
In Young's double slit experiment, the condition for the mth dark fringe is path difference = (2m+1)λ/2. For m = 2, the path difference is:
- A. 5λ/2
- B. 3λ/2
- C. 7λ/2
- D. 9λ/2
Answer: A. 5λ/2
Substituting m = 2 in (2m+1)λ/2 gives (2×2+1)λ/2 = 5λ/2, which corresponds to the second dark fringe from the central bright fringe.
Substituting m = 2 in (2m+1)λ/2 gives (2×2+1)λ/2 = 5λ/2, which corresponds to the second dark fringe from the central bright fringe.