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.
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