Que1. Parallel light of wavelength
6563Å is incident normally on a slit 0.385 mm wide. A lens with a focal length
of 50.0 cm located just behind the slit brings the diffraction pattern to focus
on a white screen. Find the distance from the centre of the principal maximum
to (a) the first minimum and (b) the fifth minimum.

Que2. At what angle will 650 nm
light produce a second order maximum when falling on a grating whose slits are
1.2 × 10–3 cm apart?

Que3. What is the highest spectral
order that can be seen if a grating with 6000 lines / cm is illuminated by a
source of 650 nm wavelength? (Assume normal incidence.)

Que4. What is the least separation
between wavelengths that can be resolved near 640 nm in the

second order, using a diffraction
grating that is 5 cm wide and ruled with 32 lines per millimetre?

Que5. A monochromatic light of
wavelength 6000×10−8 cm is diffracted by a single slit kept at

a distance of 100 cm from the
screen. The first diffracted minimum appears at a distance of 1

mm from the central maximum. Find
the width of the slit.

Que6. There are 15,000 lines per
inch in a grating. What is the maximum number of order

obtained by using light of
wavelength 6000 Å?

Que7. Find the resolving power of a
grating having 6000 lines/cm in the fi rst-order diffraction.

The ruled length of the grating is
15 cm.

Que8. Find the minimum number of
lines required in a grating to resolve two spectral lines of

wavelength 5890 Å & 5896 Å in
the second-order diffraction.

Que9. A parallel beam of
monochromatic light is incident normally on a plane transmission

grating having 1250 lines/cm and a
second order spectral line is observed at 30o. Calculate the

wavelength of spectral line.

Que10. How many orders will be
visible if the wavelength of incident radiation is 5893oA and

the number of lines on grating is
2540/inch.