Optics Answers

In Newton's ring experiment the diameter of bright ring is reduced to 0.8 of its value after introducing a liquid below the convex surface.calculate the refractive index at liquid.

A double slit interference pattern is produced by a parallel beam of light passing through two slits of unequal widths 20 λ and 40 λ, respectively, where λ is the wavelength of the light used. The distance between the centres of the slits is 1,000 λ. If the fringes are observed on a screen far off from the slits (D >> 1,000 λ), calculate the separation of two adjacent maxima.

The electrical breakdown in air occurs at electric field strength of 3.5MV/m
.
Calculate the corresponding intensity of a plane wave.

A plane wave of wavelength 600 nm falls on a long narrow slit of width 0.6 mm.
(i) Calculate the angles of diffraction for the first two minima. (ii) How are these angles influenced if the width of slit is changed to 0.2 mm? (iii) If a convex lens of focal length 0.2 m is now placed after the slit, calculate the separation between the second minima on either side of the central maximum. (10)
b) For the arrangement described in above, repeat the calculations for the first two maxima on either side of the central maximum.

A Plano-convex lens of radius 1.0 m is placed on an optically flat glass plate and is illuminated by an extended monochromatic source. Assume that the point of contact is perfect. The diameters of the 15th and 5th dark rings in the reflected light are
5.90X10−3 m × and 3.36 X10−3 m. Next, the space between the lens and the glass plate is filled with a liquid. The diameter of the 5th ring changes to 3.0X10−3 m. Calculate the refractive index of the liquid when the ring is (i) dark, and (ii) bright, if the wavelength of light is 589 nm

A double slit interference pattern is produced by a parallel beam of light passing through two slits of unequal widths 20 λ and 40 λ, respectively, where λ is the wavelength of the light used. The distance between the centres of the slits is 1,000 λ. If the fringes are observed on a screen far off from the slits (D >> 1,000 λ), calculate the separation of two adjacent maxima.

A certain optical fibre has attenuation of 3.5db/km at 850 nm. if 0.5 nW of optical fibre is launched into the fibre, what is the power level in mW after 4 km ?

An electromagnetic wave emitted by a source travels 21km to arrive at a receiver. while travelling in another path is reflected from a surface at 19km away and travels further 12 km to reach the same receiver. If destructive interference occurs at the receiving end the maximum wavelength of the wave is 1) 5km 2) 1km 3) 5km 4) 10 k m

A microwave detector is located at the shore of a lake at a height d above the water level. As a radio star emitting monochromatic microwaves of wavelength \lambda rises slowly above the horizon, the detector indicates successive maxima and minima of signal intensity.

(a) What is the difference in phase between Ray 1 and Ray 2 arriving at the detector (in terms of d, \lambda , and \theta )?

(b) At what angle \theta above the horizon is the radio star when the first maximum is received (in terms of d and \lambda )?

A mixture of polarised & unpolarised is incident on a polariser. As the polariser is rotated through 360°, it is found that the minimum & maximum of the transmitted intensity is in the ratio 1:q. The ratio of intensities of polarised to unpolarised light in the incident beam is =?