An object is placed 21 cm in front of a concave mirror of radius of curvature 10cm. A glass slabe of thickness 3cm and refractive index 1.5 is then placed close to the irror in the space between the object and the mirror. The distance of the near surface of the slabe from the mirror is 1cm. The final image from the mirror will be formed at

Explanation

To solve the problem step by step, we will follow the sequence of events as described in the video transcript.

### Step 1: Identify the given values
- Object distance (u) = -21 cm (the negative sign indicates that the object is in front of the mirror)
- Radius of curvature (R) = -10 cm (for a concave mirror, R is negative)
- Thickness of the glass slab (t) = 3 cm
- Refractive index of the glass slab (μ) = 1.5
- Distance of the near surface of the slab from the mirror = 1 cm
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