# MCQ Questions for Class 12 Physics Chapter 10 Wave Optics with Answers

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## Wave Optics Class 12 MCQs Questions with Answers

Solve this Wave Optics Multiple Choice Questions of Class 12 Physics Chapter 10 MCQ, so as not to miss out on any concept from being clear about what they mean!

Question 1.
In a Young’s doubles-slit experiment, the source is white light. One of the holes is covered by a red filter and another by a blue filter. In this case
(a) there shall be alternate interference patterns of red and blue.
(b) there shall be an interference pattern for red distinct from that for blue.
(c) there shall be no interference fringes.
(d) there shall be an interference pattern for red mixing with one for blue.

Answer: (c) there shall be no interference fringes.

Question 2.
Figure shows a standard two-slit arrangement with slits S1, S2. P1, P2 are the two minima points on either side of P (figure). At P2 on the screen, there is a hole and behind P2 is a second 2-slit arrangement with slits S3, S4 and a second screen behind them.

(a) There would be no interference pattern on the second screen but it would be lighted.
(b) The second screen would be totally dark.
(c) There would be a single bright point on the second screen.
(d) There would be a regular two-slit pattern on the second screen.

Answer: (d) There would be a regular two-slit pattern on the second screen.

Question 3.
In a Young’s double-slit experiment, the slits are separated by 0.28 mm and the screen is placed 1.4 m away. The distance between the central bright fringe and the fourth bright fringe is measured to be 1.2 cm. Determine the wavelength of light used in the experiment.
(a) 500 nm
(b) 600 nm
(c) 700 nm
(d) 600 Å

Question 4.
In Young’s double-slit experiment the separation d between the slits is 2 mm, the wavelength X of the light used is 5896 A and distance D between the screen and slits is 100 cm. It is found that the angular width of the fringes is 0.20°. To increase the fringe angular width to 0.21° (with same λ and D) the separation between the slits needs to be changed to:
(a) 1.8 mm
(b) 1.9 mm
(c) 2.1 mm
(d) 1.7 mm

Question 5.
The angular width of the central maximum in a single-slit diffraction pattern is 60°. The width of the slit is 1 mm. The slit is illuminated by monochromatic plane waves. If another slit of same width is made near it, Young’s fringes can be observed on a screen placed at a distance 50 cm from the slits. If the observed fringe width is 1 cm, what is slit separation distance? (i.e. distance between the centres of each slit)
(a) 50 mm
(b) 75 mm
(c) 100 mm
(d) 25 mm

Question 6.
Two coherent point sources S1 and S2 are separated by a small distance ‘d’ as shown. The fringes obtained on the screen will be:

(a) points
(b) straight lines
(c) semi-circles
(d) concentric circles

Question 7.
The Young’s double-slit experiment is performed with blue and green light of wavelengths 436 nm and 546 nm, respectively. If x is the distance of 4th maxima from the central one, then
(a) xblue = xgreen
(b) xblue > xgreen
(c) xblue < xgreen
(d) xblue / xgreen

Question 8.
In a Young’s double-slit experiment, slits are separated by 0.5 mm, and the screen is placed 150 cm away. A beam of light consisting of two wavelengths, 650 nm and 520 nm, is used to obtain interference fringes on the screen. The least distance from the common central maximum to the point where the bright fringes due to both the wavelengths coincide is:
(a) 9.75 mm
(b) 15.6 mm
(c) 1.56 mm
(d) 7.8 mm

Question 9.
An interference pattern is observed by Young’s double-slit experiment. If now the separation between coherent sources is halved and the distance of screen from coherent sources is doubled, then fringe width
(a) becomes double
(b) becomes one-fourth
(c) remains same
(d) becomes four times

Question 10.
A linear aperture whose width is 0.02 cm is placed immediately in front of a lens of focal length 60 cm. The aperture is illuminated normally by a parallel beam of wavelength 5 × 10-5cm. The distance of the first dark band of the diffraction pattern from the centre of the screen is:
(a) 0.20 cm
(b) 0.15 cm
(c) 0.10 cm
(d) 0.25 cm

II. Fill in the blanks

Question 1.
Light has …………….. nature.

Question 2.
According to Huygen’s principle all points on a given wavefront are taken as ………………

Question 3.
A spherical wavefront Is due to a …………….. source of light.

Question 4.
For sustained interference of light the waves emitted by the two sources must have a ………………… phase difference.

Question 5.
Two independent sources ……………….. produce sustained interference.

Question 6.
In Young’s double slit experiment, the fringe width is given by ………………..

Question 7.
Fringe width is different as the separation between two consecutive ………………… or ………………

Question 8.
Continuous locus of oscillation with constant phase is called ………………

Question 9.
……………… of light occurs when size of the obstacle of aperture is comparable of wavelength of light.

Question 10.
In interference and ……………….., the light energy is redistributed which increases in one region and decreases in other.

Question 11.
Poloroid is a device to produce and detect ……………….. polorised light.

Question 12.
A beam of light is incident normally upon a polariser and the intensity of emergent beam is l0. The intensity of the emergent beam is found to be unchanged when the polariser is rotated about an axis perpendicular to the pass axis. Incident beam is ……………….. in nature.

Question 13.
Polarisation phenomenon are exhibited by the …………………. waves only.

Question 14.
The value of Brewster Angle depends on the nature of the transparent refracting medium and the ………………….. of light used.

Question 15.
At polarising angle the refracted and reflected are ……………….. to each other.

Question 16.
The intensity in sunglasses and window panes can be controlled by ……………….