Fill in the blanks:
Q: Critical angle is the angle of ____in denser medium for which the angle of ____in rarer medium is ____-

Answer

To fill in the blanks for the question regarding the critical angle, we will follow these steps:

1. **Understanding the Definition**: The critical angle is defined as the angle of incidence in a denser medium that results in an angle of refraction of 90 degrees in a rarer medium.

2. **Identifying the Terms**:
- The first blank refers to the angle of incidence in the denser medium.
- The second blank refers to the angle of refraction in the rarer medium.
- The third blank refers to the specific angle that the second blank equals, which is 90 degrees.

3. **Filling in the Blanks**:
- The first blank: "incidence"
- The second blank: "refraction"
- The third blank: "90 degrees"

Putting it all together, we get:
- Critical angle is the angle of **incidence** in denser medium for which the angle of **refraction** in rarer medium is **90 degrees**.

### Final Answer:
Critical angle is the angle of **incidence** in denser medium for which the angle of **refraction** in rarer medium is **90 degrees**.

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