4. In a biprism experiment, fifteenth dark band is observed at 3.5 mm from the central bright band when red light of wavelength 6400 A° is used. Keeping the arrangement undisturbed, red light is substituted by blue light of wavelength 4800 A°. What will be the new fringe width?

2. A plane-wave, monochromatic beam traveling in a medium with index of refraction ni is incident at angle 0; on the plane boundary surface of a medium with index of refraction n2 < nị and undergoes total internal reflection. (i) Show that the beam penetrates the second medium to a depth of order L = njwVsin? 0; – sin² 0. where 0, is the critical angle and w is the frequency.

32. Light of wavelength 630 nm is incident on a long, narrow slit. Determine the angular deflection of the first diffraction minimum if the slit width is (a) 0.020 mm, (b) 0.20 mm, and (c) 2.0 mm.

1)A red low-power laser with λ = 634nm was beamedat a double-slit grating. An interference patternappeared on a screen 2.50 m from the grating. Thedistance from central spot to the next bright spotwas 22.5cm.What is the spacing between the slits in the grating? 2. The red laser (in Q1) is replaced by a blue laserwith a shorter wavelength. All else is the same.Show mathematically whether the interferencepattern it produces will place the bright spots closeror further apart. 3.Given that the blue laser in Q2 has a wavelength of445 nm, calculate the “spot-spacing” for the sameslit grating and screen distance as in Q1. 4.A green laser beam produces spots which are0.334m apart (central to m=1) when a grating is usedwith slits 3,000 nm apart and a screen 1.90m away.What is the wavelength of the laser light?