To solve this problem we will convert the values given to international units (meters) and then proceed to calculate the number of wavelengths through the division of the width over the wavelength. This is,
[tex]\lambda = 650 nm =650 * 10^{-9} m[/tex]
[tex]w_1 = 0.16 mm = 0.16 * 10^{-3} m[/tex]
[tex]w_2 = 0.04 mm =0.04 * 10^{-3} m[/tex]
Now the number of wavelengths is the division between the total width over the wavelength therefore
First case,
[tex]\frac{w_1}{\lambda} = \frac{ 0.16 * 10^{-3}}{650 * 10^{-9}} = 4062.5 * 10^6[/tex]
Second case,
[tex]\frac{w_2}{\lambda} = \frac{0.04 * 10^{-3} }{650 * 10^{-9} } = 16250 * 10^6[/tex]
