# WBUT Solved Previous Year Question Papers CS Holography

Holography is based on

[WBUT 2010 (DECEMBER)]

a)               the interference of reference and object waves which, are coherent

b)              superposition of object and the reference waves which are of slightly different wavelengths                                                             ,

c)                recording of superposed images of two different wavelengths

d)               recording the phase information of the resultant of the reference and the object

1.2 In holography, the 3D images are

a)     interference

c)      polarization

Answer; (a) obeying the principle of

b)      diffraction {WBUT 2011 (JUNE)]

d)      dispersion

3. Which of the following statements is not true about reconstruction of the holographic image?                                                                       [WBUT 2011 (DECEMBER)]

(a)     The hologram must be illuminated with a partially incoherent light

(b)        Both real image and virtual image are formed

(c)      The frequency of the virtual image are formed

(d)       The reconstructed image is a virtual image Answer: (a)             .

1-                 4. For holography system, the exposure time is of the order of

a)     5 seconds and depends on the colour of the object [WBUT 2012(JUNE)]

b)       nearly 2 seconds                    c) 1 second          d) 50 seconds

2.1.    Explain how holographic images one reconstructed from the holograms.

.                                                                                   [WBUT 2010(DEC EMBER)]

Hologram

Holographic image reconstruction from hologram is shown in the figure. An observer looking through the hologram sees a perfect three-dimensional image. This image exhibits, as shown in figs. all the effects of perspective, and depth of focus when photographed, that characterized the original object.

–                                                                                                ^                                                                                                                             ”                                         ‘v

2-2- Why Is ft necessary that Hie object beam and reference beam in holography are highly coherent?                                                               [WBUT 2011 (JUNE)]

In recording process of a hologram, a beam of coherent light from a laser is split into two beams by a semi transparent mirror. The transmitted beam is known as reference beam and the reflected beam is known as object beam. The reference beam falls directly on the film, whereas the object beam is scattered by the object, to be photographed. These two ■ beam form interference pattern on the film. As we know the basic condition for getting interference the two superposing beams must be coherent. So to get the interference patterns reference beam and object beam are highly coherent.

2-                                                                                                                                                                                                                                                                                                                                     3- Describe how the phase information of an object wave may be recorded in a holographic plate.                                                               [WBUT 2011 (DECEMBER)]

By converting the changes of phase into changes of intensity through interfemce phase

information is recorded. A laser beam is split into two beams by a beam splitter. One

beam is scattered by the object and is called the object wave. The other beam is called the

reference wave. The object wave and the reference wave are made to interfere. The

interference fringes, characteristic of the object are formed. This interference pattern has

in it not only the amplitude distribution but also the phase of the electromagnetic wave

scattered by the object. Since the intensity pattern has both the amplitude and phase

recorded in it. The hologram has little resemblance to the object. It has in it a coded form of the object wave.