Write one condition where it does not bend when entering a medium of different optical density.

Explanation

**Step-by-Step Solution:**

1. **Understanding Refraction**: Refraction is the bending of light as it passes from one medium to another with a different optical density. This bending occurs due to a change in the speed of light in different media.

2. **Normal Incidence**: When light strikes the boundary between two media at an angle of 90 degrees (perpendicular to the surface), it is said to be entering the medium normally.

3. **Condition for No Bending**: The specific condition where light does not bend when entering a medium of different optical density is when it enters normally. In this case, the angle of incidence is 0 degrees.

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