Question

Consider sunlight incident on a slit of width ${10}^3\mathring{A}$. The image seen through the slit shall,

• A. be a fine sharp slit, white in colour at the center.
• B. a bright slit, white at the center and diffusing to zero intensities at the edges.
• C. a bright slit, white at the center, diffusing to regions of different colors.
• D. only be a diffused slit, white in colour.

Answer 1

The correct option is A be a fine sharp slit, white in colour at the center.

For visible light, range of wavelengths is, $\lambda =3900\mathring{A}$ to $7000\mathring{A}$.
Given width of the slit is, $a={10}^3\mathring{A}=1000\mathring{A}$.

Thus, as $a<\lambda$, no diffraction occurs.
The image seen through the slit shall be a fine sharp slit, white in colour at the center.

Hence, (A) is the correct answer.

Why this question? To be able to decide, whether, diffraction will occur in a given situation.