A transparent film of refractive index, 2.0 is coated on a glass slab… | JEE Main 2025 (22 Jan, Shift 2)

Q10JEE Main 2025 · 22 JAN · SHIFT 2Medium

Biprism, Thin Films & Other Devices

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.]

Show answer and solution

Answer: (b)

Maximum transmission means minimum reflection.
Air to film (1 to 2.0): phase change $\pi$ ; film to glass (2.0 to 1.45): no phase change.
With one $\pi$ shift, reflection is minimum when $2\mu t = m\lambda$ ; least $t = \frac{\lambda}{2\mu}$ .
$t = \frac{550}{2\times 2.0} = 137.5\ \text{nm}$ . So the answer is (b).

Report a mistake

More questions on Biprism, Thin Films & Other Devices

A ray of light of intensity ' I ' is incident on a parallel glass slab at a point ' A '…MHT CET 2025 (20 Apr, Shift 2)
A thin transparent film with refractive index 1.4, is held on circular ring of radius 1.8…JEE Main 2025 (28 Jan, Shift 2)
In biprism experiment, the fringe width is 0.6 mm. The distance between 6 th dark fringe…MHT CET 2024 (15 May, Shift 1)
In a biprism experiment, monochromatic light of wavelength ' λ ' is used. The distance…MHT CET 2024 (4 May, Shift 2)
In biprism experiment, if 5 th bright band with wavelength λ₁ coincides with 6 th dark…MHT CET 2024 (10 May, Shift 1)
A parallel beam of light of intensity I₀ is incident on a glass plate, 25% of light is…MHT CET 2024 (4 May, Shift 2)
In a biprism experiment, monochromatic light of wavelength ' λ ' is used. The distance…MHT CET 2023 (13 May, Shift 1)
In two separate setups for Biprism experiment using same wavelength, fringes of equal…MHT CET 2023 (12 May, Shift 1)

Biprism, Thin Films & Other Devices question from JEE Main 2025 (22 Jan, Shift 2)

More questions on Biprism, Thin Films & Other Devices