Write the conditions for no refraction.

For no refraction to occur when light passes from one medium to another, the following conditions must be satisfied:
1. The Angle of Incidence is Zero:
• When light strikes the interface between two media perpendicularly (at an angle of incidence = 0°), it passes straight through without changing direction.
• This occurs because the incident ray is along the normal, and there is no angular deviation, even if the refractive indices of the two media are different.
2. The Refractive Indices of the Two Media are Equal:
• If the refractive index of the two media is the same (e.g., air and vacuum, or two liquids with identical refractive indices), no bending of light occurs.
• Mathematically, using Snell's law: n1sin⁡θ1=n2sin⁡θ2n_1 \sin \theta_1 = n_2 \sin \theta_2 If n1=n2n_1 = n_2, then sin⁡θ1=sin⁡θ2\sin \theta_1 = \sin \theta_2, and the ray continues in the same direction without refraction.
3. The Medium is Uniform:
• If light travels within a single uniform medium, there is no change in the refractive index, and thus, no refraction occurs.
Summary:
No refraction occurs if:
1. The light ray strikes the boundary perpendicularly (θi=0°\theta_i = 0°).
2. The refractive indices of the two media are the same (n1=n2n_1 = n_2).
3. The light travels through a single, uniform medium.