Multiple Choice QuestionsTo observed diffraction, the size of the obstacle
should be much larger than the wavelength
has no relation to wavelength
should be of the order of wavelength
should be where λ is the wavelength
In Young's double slit experiment, the source is white light. One slit is covered with red filter and the other with blue filter. There shall be
alternate red and blue fringes
alternate dark and pink fringes
alternate dark and yellow fringes
no interference
Light of wavelength 600 nm is incident normally on a slit of width 0.2 mm. The angular width of central maxima in the diffraction pattern is (measured from minimum to minimum)
6 × 10-3 rad
4 × 10-3 rad
2.4 × 10-3 rad
4.5 × 10-3 rad
According to Huygens' principle, during refraction of light from air to a denser medium
Wavelength decreases but speed increases
Wavelength increases but speed decreases
Wavelength and speed increases
Wavelength and speed decreases
In a system of two crossed polarisers, it is found that the intensity of light from the second polariser is half from that of first polariser. The angle between their pass axes is
60°
30°
0°
45°
In Young's double-slit experiment, if yellow light is replaced by blue light, the interference fringes becomes
darker
brighter
wider
narrower
When one of the slits of Young's experiment is covered with a transparent sheet of thickness 4·8 mm, the central shifts to a position originally occupies by the 30th bright fringe. What should be the thickness of the sheet if the central fringe has to shift to the position occupied by 20th bright fringe ?
1.6 mm
3.8 mm
3.2 mm
7.6 mm
In Young's double slit experiment, the central bright fringe can be identified
as it is narrower than other bright fringes
by using white light instead of monochromatic light
as it has a greater intensity than other bright fringes
as it is wider than other bright fringes
B.
by using white light instead of monochromatic light
Interference fringes are always equally spaced and also have same intensity (Imax) as central part is always bright. If sources are given white light which consists of a number of wavelength (colour). Then light of each wavelength gives its own set of fringes and hence fringe width will be different for different λ. Only the central (zero order) fringes of all wavelengths lie in same positions for each colour. The fringes of different colours are therefore intermixed. Hence only a few coloured fringes are obtained when path difference is large. There is a very much intermixing ofcolours at any point so that the resultant colour is white and uniform illumination is obtained. Fringe pattern will disappear. Hence either the light should be monochromatic or the path difference between the interfering waves must be small. Hence in our options for answer, none is correct. (b) is insuffficient to be correct.
Switch
