Here I am posting a question of Jee Adv. 2023 based on refraction.

A monochromatic light wave is incident normally on a glass slab of thickness 𝑑, as shown in the figure. The refractive index of the slab increases linearly from 𝑛1 to 𝑛2 over the height ℎ. Which of the following statement(s) is(are) true about the light wave emerging out of the slab?

(A) It will deflect up by an angle tan^-1[(n₂²-n₁²)d/2h]

(B) It will deflect up by an angle tan^-1[(n₂-n₁)d/h]

(C) It will not deflect.

(D) The deflection angle depends only on (𝑛₂ − 𝑛₁ ) and not on the individual values of 𝑛₁ and 𝑛₂.

As per the official answer key correct answer is 2, but I am unable to understand that why light will bend if angle of incidence is zero then as per snell's law angle of refraction must be zero?

Here I am posting a question of Jee Adv. 2023 based on refraction.

A monochromatic light wave is incident normally on a glass slab of thickness 𝑑, as shown in the figure. The refractive index of the slab increases linearly from 𝑛1 to 𝑛2 over the height ℎ. Which of the following statement(s) is(are) true about the light wave emerging out of the slab?

(A) It will deflect up by an angle tan^-1[(n₂²-n₁²)d/2h]

(B) It will deflect up by an angle tan^-1[(n₂-n₁)d/h]

(C) It will not deflect.

(D) The deflection angle depends only on (𝑛₂ − 𝑛₁ ) and not on the individual values of 𝑛₁ and 𝑛₂.

As per the official answer key correct answer is 2 and 4, but I am unable to understand that why light will bend if angle of incidence is zero then as per snell's law angle of refraction must be zero?