wave-optics Question 10
Question: Q. 1. Consider sunlight incident on a slit of width $10^{4} \AA$. 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.
[NCERT Exemplar]
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Solution:
Ans. Correct option : (a)
Explanation: Given that, width of slit $10^{4} \AA=10,000 \AA$. Wavelength of visible light varies from $4,000 \AA$ to $8,000 \AA$. As the width of slit $10,000 \AA$ is comparable to that of wavelength of visible light, i.e., 8,000 $\AA$. Hence the diffraction occurs with maxima at the centre. So at the centre all colours appear, i.e., white colour appears at the centre.
