(C) The Assertion is correct because thin films exhibit interference patterns when illuminated by white light,resulting in the observation of colours.

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If the Assertion is correct but Reason is incorrect.

(C) The Assertion is correct because thin films exhibit interference patterns when illuminated by white light,resulting in the observation of colours.However,the Reason is incomplete and therefore incorrect. The phenomenon of interference in thin films occurs due to the superposition of light waves reflected from $BOTH$ the upper surface $AND$ the lower surface of the thin film,not just the upper surface. The path difference between these two reflected rays leads to constructive or destructive interference for different wavelengths,which creates the observed colours.

Class 12 Physics Wave Optics Thin film Interference, fresnel biprism, lloyd's mirror

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Assertion: Thin films such as a soap bubble or a thin layer of oil on water show beautiful colours when illuminated by white light.
Reason: It happens due to the interference of light reflected from the upper surface of the thin film.

AIIMS 2002 All AIIMS

A
If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
B
If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
C
If the Assertion is correct but Reason is incorrect.
D
If both the Assertion and Reason are incorrect.

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Wave Optics

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Thin film Interference, fresnel biprism, lloyd's mirror

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Light is incident on a glass plate $(\mu = 1.5)$ such that the angle of refraction is $60^\circ$. $A$ dark band is observed corresponding to a wavelength of $6000 \, \mathring A$. If the thickness of the glass plate is $1.2 \times 10^{-3} \, mm$,find the order of the interference band.

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In a biprism experiment,a steady interference pattern is observed on the screen using light of wavelength $\lambda_1 = 5000 \ Å$. Without disturbing the setup of the experiment,the source of light is replaced by a source of wavelength $\lambda_2 = 6400 \ Å$. The fringe width will:

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In a biprism experiment, the $4^{th}$ dark band is formed opposite to one of the slits. The wavelength of light used is (where $D$ = distance between source and screen, $d$ = distance between the slits).

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

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$A$ soap film with refractive index $\mu = 4/3$ is illuminated by white light incident at an angle of $60^\circ$. $A$ dark band corresponding to a wavelength of $5500 \, \mathring{A}$ is observed in the reflected light. Find the minimum thickness of the film in $\mathring{A}$.

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Assertion: Thin films such as a soap bubble or a thin layer of oil on water show beautiful colours when illuminated by white light.Reason: It happens due to the interference of light reflected from the upper surface of the thin film.

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Light is incident on a glass plate $(\mu = 1.5)$ such that the angle of refraction is $60^\circ$. $A$ dark band is observed corresponding to a wavelength of $6000 \, \mathring A$. If the thickness of the glass plate is $1.2 \times 10^{-3} \, mm$,find the order of the interference band.

In a biprism experiment,a steady interference pattern is observed on the screen using light of wavelength $\lambda_1 = 5000 \ Å$. Without disturbing the setup of the experiment,the source of light is replaced by a source of wavelength $\lambda_2 = 6400 \ Å$. The fringe width will:

In a biprism experiment, the $4^{th}$ dark band is formed opposite to one of the slits. The wavelength of light used is (where $D$ = distance between source and screen, $d$ = distance between the slits).

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

$A$ soap film with refractive index $\mu = 4/3$ is illuminated by white light incident at an angle of $60^\circ$. $A$ dark band corresponding to a wavelength of $5500 \, \mathring{A}$ is observed in the reflected light. Find the minimum thickness of the film in $\mathring{A}$.

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Assertion: Thin films such as a soap bubble or a thin layer of oil on water show beautiful colours when illuminated by white light.
Reason: It happens due to the interference of light reflected from the upper surface of the thin film.