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NCERT Class 10 Science Light – Reflection and Refraction: In-text questions (page 145) Solutions
AI-written, checked on 23 Oct 2026
Solutions written by Shishya, checked — not the board's official answers
Step-by-step working for every question of In-text questions (page 145) in NCERT's Class 10 Science book, chapter “Light – Reflection and Refraction”, written by Shishya. Each question is in our own short words; open the NCERT chapter for the exact wording and figures.
How these were checked: the solutions were drafted with AI and then read and corrected on 23 Oct 2026. Every numerical final answer is recomputed from the question's own numbers by a calculator check that runs before each release; proofs and explanations were read, not machine-checked. The NCERT textbook is the authority — if something here disagrees with it, follow the book.
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In-text (page 145) Q1
Find the focal length of a convex mirror whose radius of curvature is 32 cm.
- The radius of curvature (R) of the mirror is given as 32 cm.
why?
For a spherical mirror the focal length is half the radius of curvature: f = R/2.
- For a spherical mirror, the focal length (f) is half of the radius of curvature.
why?
For a spherical mirror the focal length is half the radius of curvature: f = R/2.
- Using the relation f = R / 2, we substitute the value of R.
why?
For a spherical mirror the focal length is half the radius of curvature: f = R/2.
- f = 32 cm / 2.
- f = 16 cm.
Answer: 16 cm
- The radius of curvature (R) of the mirror is given as 32 cm.
In-text (page 145) Q2
A concave mirror gives a real image three times the size of an object placed 10 cm in front of it. Where is the image?
- Given: object distance u = -10 cm, magnification m = -3 (real image is inverted).
why?
Magnification m = height of image ÷ height of object (= −v/u for a mirror, v/u for a lens). A negative m means a real, inverted image; a positive m a virtual, erect one.
- Use the magnification formula m = -v/u.
why?
Magnification m = height of image ÷ height of object (= −v/u for a mirror, v/u for a lens). A negative m means a real, inverted image; a positive m a virtual, erect one.
- Substitute values: -3 = -v / (-10).
- Simplify: -3 = v / 10.
- Solve for v: v = -30 cm.
- The negative sign indicates the image is formed in front of the mirror.
Answer: v = -30 cm; 30 cm in front of the mirror
- Given: object distance u = -10 cm, magnification m = -3 (real image is inverted).
Other exercises in this chapter
- In-text questions (page 142) — 4 questions
- In-text questions (page 150) — 5 questions
- In-text questions (page 158) — 3 questions
- End-of-chapter exercises — 17 questions
← Light – Reflection and Refraction: notes, practice and all exercises
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