Question

E . The red light of wavelength 750 nm and blue light of 450 nm are illuminating a film of n=1.2 surrounded by the air.

a). What is the minimum thickness of this film which will provide the maximum reflection for both these wavelengths? Give answer in nm. (IT IS A SINGLE ANSWER, NOT TWO INDIVIDUAL)

b). The next after minimum thickness of the film which provides maximum reflection for both wavelengths in the previous question will be? Give answer in nm. IT IS A SINGLE ANSWER, NOT TWO INDIVIDUAL)

c). The minimum thickness of a film which provides the total transmission for wavelengths from question E? Give answer in nm. (IT IS A SINGLE ANSWER, NOT TWO INDIVIDUAL)

d). The next after minimum thickness which provides maximum transmission for both wavelengths from question E ? Give answer in nm. (IT IS A SINGLE ANSWER, NOT TWO INDIVIDUAL)

Answer 1

M2 = 1.2 (film) In case of reflection (nean, ) I (air) for maximum reflection! tata waredagth inside film 27-(m) as n film film So, &t - (m) in t- thickness of film order of reflection e mt m = 1,2,3

nfilm analm 4x1.2 150x100m uxl.2 t. 122*9 (i) at = (m-1) for mal 2t=1 ta j t = (a) (for red light) t = 156.25x10 m = 0.156816'm 0.156pm/ forred light (b) a= usox lom 93.75 X 10m t = 0.0937pm) for blue light. So, minimum thickness required is t=0 1564m C) for next order sofledion (2-4) 1 t = 3xd 4 1.2 it = 3 x 2 = 3x 750nm uxl.2 maze at = (for red lights 4 it = 0.468um 7 for red light t = 3 x uronm 4x1.2 -0.3748 Him for blue light.

So, thickness required in It =0.4683m) (it) for total focansmistion:- om=1, 2, 3 . [2t = min 2 tnfilm -md (a) for mal tad ta - Tronm 2x1,2 - 0.3125 m 2x1.2 t= .3125pm for red light (6) it - usonm 22 X 1,2 0.1875,4m it = 0.1875um? - for blue light Now; thickness required for pansmission of both t=0.3125m light is (iv) for m= 2: Net ander bansmission: at = ax d 1.2 & t=1 1.2 (a) t = 750nm = 0.625 Sum alt=0.625,4m. -red light t= 45oom & t=0.3754m) - blue light (b) Son required thickness is Litcoibosum)