A ray of light falls on a glass plate of refractive index `mu=1.5`.
What is the angle of incidence of the ray if the angle between the reflected and
refracted rays is `90^@`?

Explanation

To solve the problem, we need to find the angle of incidence of a ray of light falling on a glass plate with a refractive index of \( \mu = 1.5 \), given that the angle between the reflected and refracted rays is \( 90^\circ \).

### Step-by-Step Solution:

1. **Understand the Geometry**:
- Let \( i \) be the angle of incidence.
- According to the law of reflection, the angle of reflection \( r \) is equal to the angle of incidence, so \( r = i \).
- The angle between the reflected ray and the refracted ray is given as \( 90^\circ \).
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