Wave Optics

JEE Main 2025 (Online) 22nd January Evening ShiftMCQMedium📈 Topic in 5% papers+4−1

Ques. 1JEE Main 2025, 22 January (Evening Shift)

A transparent film of refractive index, 2.0 is coated on a glass slab of refractive index, 1.45. What is the minimum thickness of transparent film to be coated for the maximum transmission of Green light of wavelength 550 nm . [Assume that the light is incident nearly perpendicular to the glass surface.]

68.7 nm
137.5 nm
94.8 nm
275 nm

Answer

(2) 137.5 nm

Solution

[figure]

Ray 1 (air denser film): phase change ; ray 2 (film rarer glass): none

Least reflection (most transmission): 2 t=n , so t = 2 (n=1)

= 5502 2.0=137.5 nm

Answer: (2)

Keep practising — Wave Optics

Ques. 2JEE Main 2025, 22 January (Evening Shift)

Given below are two statements. One is labelled as Assertion (A) and the other is labelled as Reason (R). In the light of the above statements, choose the correct answer from the options given below :

(A) is true but (R) is false
Both (A) and (R) are true and (R) is the correct explanation of (A)
(A) is false but (R) is true
Both (A) and (R) are true but (R) is NOT the correct explanation of (A)

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