Question

state the condition under which no change in the direction of propagation of light rays would take place when it passes from medium a to medium b

Answer 1

If the incident ray follows the normal drawn perpendicularly on the junction plane of 2 mediums, it will not refract.

Practically in above scenario, the angle of incidence (angle between the incident ray and the normal), 'i' becomes 0

when i = 0

Angle of refraction (angle between the refracted ray and the normal), 'r' also becomes 0 thus no change in direction occurs.

Answer 2

incident ray should fall on the medium B at 0° (perpendicularly)from medium A.

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