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JEE Main 2026 · 4 Apr · Shift 1, Physics question 45

An unpolarized light is incident on the plane interface of air-dielectric medium shown in figure. If the incident angle is equal to Brewster angle, identify the expression representing reflected wave.

Axes: x along the interface (pointing back), y along the interface (to the right), z pointing down into the medium. Unpolarized light in air falls obliquely on the horizontal air-medium interface in the x-z plane.
Choose one option
Answer and worked solution

Official answer: A

Geometry. The light travels in the x-z plane and falls on the interface z = 0; the reflected ray goes forward in x and back up (−z), so its phase is sin⁡(kx−kz−ωt)\sin(kx-kz-\omega t). Only (A) has this.

Polarisation. At the Brewster angle the reflected light is polarised perpendicular to the plane of incidence, i.e. along y^\hat y.

Note. (A) also carries an Exi^E_x\hat i term, which is not transverse to the propagation direction i^−k^\hat i-\hat k. The physical reflected wave is Eyj^sin⁡(kx−kz−ωt)E_y\hat j\sin(kx-kz-\omega t); (A) is the keyed option because it is the only one with the correct phase and the j^\hat j component.

(A)

Topics:Polarisation and Brewster's lawProperties of EM waves
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