Science — CBSE Class 10 board question

Ray Diagram — Refraction through a Triangular Prism:

```
A
/\
/ \
N / \
| / r₁ \
→→→→→•→ → → →•→→→→→
i / refracted \ e
/ ray OO' \
B________________C
```

A ray PQ strikes face AB at angle of incidence i, refracts towards the normal (angle of refraction r₁), travels through the prism as QR, exits face AC, and bends away from the normal as RS (emergent ray).

The angle of deviation (D) is the angle between the incident ray (extended) and the emergent ray RS, marked at their point of intersection.

(Diagram must show: incident ray, two normals, refracted ray inside prism, emergent ray, and angle D labelled between extended incident ray and emergent ray.)

Source: Chapter 9 (Light – Reflection and Refraction), Refraction of Light section.

---

• The question specifically asks to draw the diagram and mark angle of deviation — both are essential for full marks.
• Angle of deviation (D) is measured between the original direction of the incident ray (produced) and the final emergent ray.
• The ray bends towards the normal on entering the denser glass medium and away from the normal on exiting.
• Label: incident ray, normal at each face, refracted ray, emergent ray, and clearly mark ∠D — missing the label loses a mark.