A thin film of thickness t and index of refraction 1.33 coats a glass with index of refraction 1.50.What is the least thickness t that will strongly reflect light with wavelength 600nm incident normally

							
Expression of Least thickness t that will strongly reflect  light:
 
since, t = nλ/2μ
 
Here,
 
λ = Wavelength = 600 nm
 
μ = Refractive index of film = 1.33
 
For least thickness : n = 1
 
Hence,
 
t = λ / 2μ
 
= 600 / 2*1.33
 
= 600/ 2.66
 
= 225.56
 
≈ 225 nm
 
Thus, least thickness t that will strongly reflect  light with wavelength 600nm incident normally is 225 nm.
 
Thanks and regards
						

							
the condition is 2μtcosr = nλ
for normal incident r = 90
hence 2μt = nλ
so,  t = nλ/2μ
Here,
λ = Wavelength = 600 nm
μ = Refractive index of film = 1.33
For least thickness : n = 1
Hence,
t = λ / 2μ
= 600 / 2*1.33
= 600/ 2.66
= 225.56
≈ 225 nm
none of the options are correct. But we can take nearest answer whic is 200nm
						

							
the condition is 2μtcosr = nλ
for normal incident r = 0 deg
hence 2μt = nλ
so,  t = nλ/2μ
Here,
λ = Wavelength = 600 nm
μ = Refractive index of film = 1.33
For least thickness : n = 1
Hence,
t = λ / 2μ
= 600 / 2*1.33
= 600/ 2.66
= 225.56
≈ 225 nm
none of the options are correct. But we can take nearest answer whic is 200nm