CBSE 2026 · Region 5 · Set 1 · Q19 · 2 marks
A tank is filled with a liquid to a height of $\displaystyle 12 \cdot 5 \mathrm{~m}$. The apparent depth of a needle lying at the bottom of the tank is measured to be $\displaystyle 9.0$ m . Calculate the speed of light in the liquid.
Marking-scheme solution
\[\begin{aligned}
& \mathrm{n}=\frac{\text { speed of light in }}{\text { speed of light in }} \\
& \mathrm{n}=\frac{\text { real depth }}{\text { apparent depth }} \\
& \mathrm{n}=\frac{12.5}{9} \ldots \ldots \ldots \ldots . \\
& \begin{aligned}
\mathrm{r} & =\frac{3 \times 10^{8} \times 9}{12.5} \\
& =2.16 \times 10^{8} \mathrm{~m} / \mathrm{s}
\end{aligned}
\end{aligned}
\]
Ray Optics and Optical InstrumentsRefractionApplyvery_short_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 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.