$A$ mixture of yellow light of wavelength $580 \ nm$ and blue light of wavelength $450 \ nm$ is incident normally on an air film of thickness $2.9 \times 10^{-4} \ mm$. The colour of reflected light is

$A$ very thin transparent film (like a soap bubble) is viewed in white light. The color of the film appears .......

In a Fresnel biprism experiment,the eyepiece is placed at a distance of $120 \, cm$ from the source. The distance between the two virtual images is found to be $0.075 \, cm$. If the eyepiece is moved by $1.92 \, cm$ to cross $20$ fringes in the field of view,what is the wavelength of light in $\mathop A\limits^o$?

$A$ parallel beam of light of intensity $I_0$ is incident on a glass plate. $25 \%$ of light is reflected by the upper surface and $50 \%$ of light is reflected from the lower surface. The ratio of maximum to minimum intensity in the interference region of the reflected rays is

An oil film flowing on water appears coloured due to interference. For observing this effect,the approximate thickness of the oil film should be:

In a biprism experiment, the maximum intensity is $I_0$. If the path difference between the two interfering waves is $\frac{\lambda}{3}$, then the intensity at the point on the screen is [$\sin 30^{\circ} = \cos 60^{\circ} = 0.5, \sin 60^{\circ} = \cos 30^{\circ} = \sqrt{3}/2$].