Q23 of 31 Page 1

Answer the following questions:

(a) In a double slit experiment using light of wavelength 600 nm, the angular width of the fringe formed on a distant screen is 0.1°. Find the spacing between the two slits.


(b) Light of wavelength 5000 Å propagating in air gets partly reflected from the surface of water. How will the wavelengths and frequencies of the reflected and refracted light be affected?


(a) Angular width of fringe in double-slit experiment is given by


Where,


D= spacing between the slits


Given, wavelength of light A= 600 nm


Angular width of fringe,





(b) The frequency and wavelength of reflected wave will not change.


The refracted wave will have same frequency, only wavelength will change.


The velocity of light in water is given by,



Where, v= velocity of light


f= frequency of light


= wavelength of light


As light ray is travelling from rarer medium to denser medium, its speed will decrease. Hence wavelength will also decrease.


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A group of students while coming from the school noticed a box marked “Danger H.T. 2200 V” at a substation in the main street. They did not understand the utility of such a high voltage, while they argued, the supply was only 220 V. They asked their teacher this question the next day. The teacher thought it to be an important question and therefore explained to the whole class.

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