Optics Answers

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 =?

Prove that the coherence length is related bu bandwidths following equation:-
L=c/∆v= λ²/∆λ

Explain how a tube of glass in a fiber optic cable can keep a beam of light reflecting inside of it, even though the glass is transparent to the light.

Green light with a wavelength of 580nm goes through a pair of slits, travels at a 30° degree angle from the slits, and ends on a screen. The slits are 0.00001914 m apart. Will the fringe on the screen show constructive or destructive interference? (Tip: Don’t round any of the numbers while doing your calculations)

A chunk of zircon is sitting in an open container of benzene. A 589nm wavelength of light has gone through the zircon and is emerging into the benzene. It strikes the boundary at an angle of 10.0° from the normal.
How would it be different if the light entered the benzene at a greater angle?
How would it be different if the benzene at an angle greater than the critical angle?

A telescope has an objective of focal length 50 cm and eyepiece of focal length 5 cm. The least distant of distinct vision is 25 cm. The telescope is focussed for distinct vision on a scale 200 cm away from the object. Calculate the magnification produced?
1)4
2)-8
3)+8
4)-2