Chapter 10: Wave Optics

Consider a light beam incident from air to a glass slab at Brewster’s angle as shown in the figure.

A polaroid is placed in the path of the emergent ray at point P and rotated about an axis passing through the centre and perpendicular to the plane of the polaroid

(a) For a particular orientation, there shall be darkness as observed through the polaroid

(b) The intensity of light as seen through the polaroid shall be independent of the rotation

(c) The intensity of light as seen through the Polaroid shall go through a minimum but not zero for two orientations of the polaroid

(d) The intensity of light as seen through the polaroid shall go through a minimum for four orientations of the polaroid

Consider sunlight incident on a slit of width 10⁴ A. The image seen through the slit shall

(a) be a fine sharp slit white in colour at the centre

(b) a bright slit white at the centre diffusing to zero intensities at the edges

(c) a bright slit white at the centre diffusing to regions of different colours

(d) only be a diffused slit white in colour

Consider a ray of light incident from air onto a slab of glass (refractive index n) of width d, at an angle θ. The phase difference between the ray reflected by the top surface of the glass and the bottom surface is

(a)

(b)

(c)

(d)

In a Young’s double-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

The figure shows a standard two-slit arrangement with slits S1, S2. P1, P2 are the two minima points on either side of P. 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

Two sources S1 and S2 of intensity I 1 and I 2 are placed in front of a screen in the figure (a). The pattern of intensity distribution seen in the central portion is given by the figure (b). In this case which of the following statements are true.

Consider sunlight incident on a pinhole of width 103A. The image of the pinhole seen on a screen shall be

(a) a sharp white ring

(b) different from a geometrical image

(c) a diffused central spot, white in colour

(d) diffused coloured region around a sharp central white spot

Consider the diffraction pattern for a small pinhole. As the size of the hole is increased

(a) the size decreases

(b) the intensity increases

(c) the size increases

(d) the intensity decreases

For light diverging from a point source

(a) the wavefront is spherical

(b) the intensity decreases in proportion to the distance squared

(c) the wavefront is parabolic

(d) the intensity at the wavefront does not depend on the distance

Is Huygen’s principle valid for longitudinal sound waves?