When a compact disc is illuminated by a source of white light,coloured 'lanes' are observed. This is due to

In a single slit diffraction pattern, the wavelength of light used is $628 \text{ nm}$ and slit width is $0.2 \text{ mm}$. The angular width of the central maximum is $\alpha \times 10^{-2} \text{ degrees}$. The value of $\alpha$ is . . . . . . . (Take $\pi = 3.14$)

At the first minimum adjacent to the central maximum of a single-slit diffraction pattern,the phase difference between the Huygens' wavelet from the edge of the slit and the wavelet from the midpoint of the slit is

If a classroom door is open just a small amount, we can hear sounds coming from the room but we can't see what is going on inside the room because

The first diffraction minima due to a single slit diffraction is at $\theta = 30^o$ for a light of wavelength $5000 \,\mathring{A}$. The width of the slit is

In a single slit diffraction pattern,a light of wavelength $6000 \mathring A$ is used. The distance between the first and third minima in the diffraction pattern is found to be $3 \text{ mm}$ when the screen is placed $50 \text{ cm}$ away from the slit. The width of the slit is . . . . . . $\times 10^{-4} \text{ m}$.