Advertisements
Advertisements
प्रश्न
A parallel beam of light of wavelength 560 nm falls on a thin film of oil (refractive index = 1.4). What should be the minimum thickness of the film so that it strongly reflects the light?
Advertisements
उत्तर
Given:-
Wavelength of light used,
\[\lambda = 560 \times {10}^{- 9} m\]
Refractive index of the oil film, \[\mu = 1 . 4\]
Let the thickness of the film for strong reflection be t.
The condition for strong reflection is
\[2\mu t = \left( 2n + 1 \right)\frac{\lambda}{2}\]
\[ \Rightarrow t = \left( 2n + 1 \right)\frac{\lambda}{4\mu}\]
where n is an integer.
For minimum thickness, putting n = 0, we get
\[t = \frac{\lambda}{4\mu}\]
\[ = \frac{560 \times {10}^{- 9}}{4 \times 1 . 4}\]
\[ = {10}^{- 7} m = 100 nm\]
Therefore, the minimum thickness of the oil film so that it strongly reflects the light is 100 nm.
APPEARS IN
संबंधित प्रश्न
If we put a cardboard (say 20 cm × 20 cm) between a light source and our eyes, we can't see the light. But when we put the same cardboard between a sound source and out ear, we hear the sound almost clearly. Explain.
Is it necessary to have two waves of equal intensity to study interference pattern? Will there be an effect on clarity if the waves have unequal intensity?
The speed of light depends ____________ .
The equation of a light wave is written as \[y = A \sin\left( kx - \omega t \right).\] Here, `y` represents _______ .
When light propagates in vacuum, there is an electric field as well as a magnetic field. These fields ____________ .
(a) are constant in time
(b) have zero average value
(c) are perpendicular to the direction of propagation of light.
(d) are mutually perpendicular
Three observers A, B and C measure the speed of light coming from a source to be νA, νBand νC. A moves towards the source and C moves away from the source at the same speed. B remains stationary. The surrounding space is water everywhere.
(a) \[\nu_A > \nu_B > \nu_C\]
(b) \[\nu_A < \nu_B < \nu_C\]
(c) \[\nu_A = \nu_B = \nu_C\]
(d) \[\nu_B = \frac{1}{2}\left( \nu_A + \nu_C \right)\]
The speed of yellow light in a certain liquid is 2.4 × 108 m s−1. Find the refractive index of the liquid.
Two narrow slits emitting light in phase are separated by a distance of 1⋅0 cm. The wavelength of the light is \[5 \cdot 0 \times {10}^{- 7} m.\] The interference pattern is observed on a screen placed at a distance of 1.0 m. (a) Find the separation between consecutive maxima. Can you expect to distinguish between these maxima? (b) Find the separation between the sources which will give a separation of 1.0 mm between consecutive maxima.
Find the thickness of a plate which will produce a change in optical path equal to half the wavelength λ of the light passing through it normally. The refractive index of the plate is μ.
In Young’s double-slit experiment, the two coherent sources have different intensities. If the ratio of the maximum intensity to the minimum intensity in the interference pattern produced is 25:1, what is the ratio of the intensities of the two sources?
A parallel beam of green light of wavelength 550 nm passes through a slit of width 0.4 mm. The intensity pattern of the transmitted light is seen on a screen that is 40 cm away. What is the distance between the two first-order minima?
When light travels from an optically rarer medium to an optically denser medium, the speed decreases because of change in ______
Light follows wave nature because ______
The path difference between two waves meeting at a point is (11/4)λ. The phase difference between the two waves is ______
A Plane Wavefront of light of wavelength 5500 A.U. is incident on two slits in a screen perpendicular to the direction of light rays. If the total separation of 10 bright fringes on a screen 2 m away is 2 cm. Find the distance between the slits.
Light behaves as _________.
Emission and absorption is best described by ______.
A ray is an imaginary line ______.
State the theories which were proposed to explain nature of light.
