CBSE Class 10 Science 2025: question 13
Set in the CBSE Class 10 board exam of 2025, paper 31/2/1, section A, question 13, for 1 mark. Try it first; the hints and our step-by-step solution are below.
Q13 · 1 mark · MCQLight – Reflection and Refraction
In the given figure the angle of incidence and the angle of deviation respectively are :
- (A)1 and 5
- (B)7 and 6
- (C)7 and 4
- (D)1 and 6
Figure in the paper: A triangular glass prism with a ray entering from the lower left face, refracting and travelling inside parallel to the base, then emerging from the right face. Dashed normals are drawn at both refracting faces. Angles marked 1 (between incident ray and normal at left face, outside), 2 (inside, between refracted ray and normal at left face), 3 (inside, at right face), 4 (between emergent ray and normal at right face), 5 (outside, at right face), 6 (between the internal ray extended and the apex-side dashed line), and 7 (between incident ray and left face of prism). See it in the official paper.
Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/2/1.
Hints
Open one hint at a time and try again before the next.
Hint 1
Angles of incidence are measured from the normal, not from the surface.
Hint 2
Deviation is between the incident direction and the emergent direction.
Step-by-step solution
Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.
The angle of incidence is the angle between the incident ray and the normal at the first face. From the figure, this is angle 1. (Angle 7 is measured from the face of the prism, not the normal.)
The angle of deviation is the angle between the incident ray extended forward and the emergent ray extended backward. In the figure, this is angle 6.
- 1 mark
So the answer is (D) 1 and 6.
Answer: (D) 1 and 6
Where the marks are
- Identifies angle 1 as incidence and angle 6 as deviation, option (D) (1 mark)
Revise the chapter
- Chapter: Light – Reflection and Refraction (notes, formulas, where marks are lost and every past question)
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The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.