On the radio, Dwayne hears reports of strange lights being seen. In order to pre

Question

On the radio, Dwayne hears reports of strange lights being seen. In order to prevent any unwanted light coming into his house Dwayne puts a thin coating on his glass (n=1.5) windows. a) If Dwayne shines white light normal to the glass it strongly reflects blue (500nm) and red (700nm) light. Determine the minimum thickness of the coating if it has an index of refraction of 1.35. b) at this thickness, what visible wavelengths (between 400 and 750nm) would Dwayne not see reflected? On the radio, Dwayne hears reports of strange lights being seen. In order to prevent any unwanted light coming into his house Dwayne puts a thin coating on his glass (n=1.5) windows. a) If Dwayne shines white light normal to the glass it strongly reflects blue (500nm) and red (700nm) light. Determine the minimum thickness of the coating if it has an index of refraction of 1.35. b) at this thickness, what visible wavelengths (between 400 and 750nm) would Dwayne not see reflected? a) If Dwayne shines white light normal to the glass it strongly reflects blue (500nm) and red (700nm) light. Determine the minimum thickness of the coating if it has an index of refraction of 1.35. b) at this thickness, what visible wavelengths (between 400 and 750nm) would Dwayne not see reflected?

Explanation / Answer

condition for constructive interference is 2 d = m */n, n is refractive index, d thickness of the coating

       blue 500 nm   d = 500*10^-9/2*1.35 = 1.85*10^-7 m

       red 700 nm   d = 700*10^-9 /2*1.35= 2.59*10^-7 m

   difference is = 0.74 *10^-7 m

for not seeing reflected light between 400 nm to 750 nm is 2d = (m+1/2 )/n

                       = 2d*n/(m+1/2)
                       = 2*0.74*10^-7*1.35/(0.5)= 399.6 nm

           if m= 1 , = 133.2 nm
           ifm= 2 , = 79.2 nm

           only 400 nm wavelength light can not be reflected

Related Questions

Navigate

• Browse (All)
• Browse O
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.