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 Fresnel's biprism,coherent sources are obtained by ...

In a biprism experiment,the distance of the second dark fringe from the central fringe is $3 \ mm$. The distance of the sixth bright fringe from the central fringe is (in $mm$)

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

In a biprism experiment,the distance between the two sources is doubled and the distance between the slit and the eyepiece is also doubled. Then the width of the fringe is

Assertion: Newton's rings are formed in the reflected system when the space between the lens and the glass plate is filled with a liquid of refractive index greater than that of glass; the central spot of the pattern is bright.
Reason: This is because the reflection in these cases will be from a denser to rarer medium and the two interfering rays are reflected under similar conditions.