CBSE 2025 · Region 6 · Set 3 · Q25 · 3 marks
(a)A concave mirror has radius of curvature $\displaystyle 20$ cm . Calculate the distance of an object from the mirror so as to form an image of magnification -$\displaystyle 2$ . Also find the location of the image.(b)If the silver coating around the centre of a concave mirror is removed, will the mirror still form the image of an object ? Justify your answer.
(a)
A concave mirror has radius of curvature $\displaystyle 20$ cm . Calculate the distance of an object from the mirror so as to form an image of magnification -$\displaystyle 2$ . Also find the location of the image.
(b)
If the silver coating around the centre of a concave mirror is removed, will the mirror still form the image of an object ? Justify your answer.
Marking-scheme solution
(a) \(\displaystyle m=-\frac{\mathrm{v}}{u}\)
\[-2=-\frac{\mathrm{v}}{u}
\]
\[\mathrm{v}=2 u
\]
\[\frac{1}{f}=\frac{1}{\mathrm{v}}+\frac{1}{u}
\]
\[\frac{1}{-10}=\frac{1}{2 u}+\frac{1}{u}
\]
\[u=-15 \mathrm{~cm}
\]
\[\mathrm{v}=-30 \mathrm{~cm}
\]
(b) Yes, same image is formed with reduced intensity, because reflecting area get reduced and laws of reflection still hold good for remaining part of the mirror.
Ray Optics and Optical InstrumentsReflection of Light by Spherical MirrorsApplyshort_answermedium
More from Ray Optics and Optical Instruments
- Assertion: A convex lens, when immersed in a liquid, disappears. Reason ( R ): The refractive indices of…2024 · asked 3×
- A convex lens (n = 1.52) has a focal length of 15.0 cm in air. Find its focal length when it is immersed in…2024 · asked 3×
- (i) Draw a labelled ray diagram showing the formation of the image at infinity by an astronomical telescope.…2022 · asked 3×
- (i) (1) Write two points of difference between an interference pattern and a diffraction pattern. (2) Name…2023 · asked 3×
- Two transparent media of refractive indices n 1 and n 2 are separated by a spherical transparent surface. The…2022 · asked 3×
- Write two necessary conditions for total internal reflection. Two prisms ABC and DBC are arranged as shown in…2022 · asked 3×
- (i) Define SI unit of power of a lens. (ii) A plano convex lens is made of glass of refractive index 1.5. The…2022 · asked 3×
- (i) An object is placed 30 cm from a thin convex lens of focal length 10 cm. The lens forms a sharp image on…2025 · asked 3×
CBSE Class 12 Physics past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.