Light appears to travel in straight lines since

Red light of wavelength $625 \, nm$ is incident normally on an optical diffraction grating with $2 \times 10^{5} \, \text{lines}/m$. Including the central principal maxima, how many maxima may be observed on a screen which is far from the grating?

Light of wavelength $6000 \, \mathring{A}$ is incident on a single slit of width $0.3 \, mm$. The angular position of the first minima will be

How will the diffraction pattern change when yellow light is replaced by blue light? The fringes will be

Light of wavelength $5000 \, \mathring{A}$ is incident on a single slit such that the first minima is formed at a distance $5 \, mm$ from the centre. If the screen is placed $2 \, m$ away,then find the width of the slit in $mm$.

The condition for obtaining secondary maxima in the diffraction pattern due to a single slit is: