‹ PrevQuestion 94 / 94 · latest first
✓ Board-verified
Science · 2023 · 4 marks
CBSE 2023 · Region 1 · Set 1 · Q39
Hold a concave mirror in your hand and direct its reflecting surface towards the sun. Direct the light reflected by the mirror on to a white…
Hold a concave mirror in your hand and direct its reflecting surface towards the sun. Direct the light reflected by the mirror on to a white card-board held close to the mirror. Move the card-board back and forth gradually until you find a bright, sharp spot of light on the board. This spot of light is the image of the sun on the sheet of paper; which is also termed as "Principal Focus" of the concave mirror.
(a)
List two applications of concave mirror.
(b)
If the distance between the mirror and the principal focus is $\displaystyle 15$ cm, find the radius of curvature of the mirror.
(c)
Draw a ray diagram to show the type of image formed when an object is placed between pole and focus of a concave mirror.
OR
(c)
An object $\displaystyle 10$ cm in size is placed at $\displaystyle 100$ cm in front of a concave mirror. If its image is formed at the same point where the object is located, find :
(i)
focal length of the mirror, and
(ii)
magnification of the image formed with sign as per Cartesian sign convention.
Marking-scheme solution
(a) Torches, search light, vehicles head lights, shaving mirrors, dentist's mirror, Solar furnaces.
(b) \(\displaystyle \mathrm{f}=15 \mathrm{~cm}\)
\[\begin{aligned}
& R=2 \mathrm{f} \\
& R=2 \times 15 \mathrm{~cm}=30 \mathrm{~cm}
\end{aligned}
\]
(c) 
(i) \(\displaystyle \mathrm{h}=+10 \mathrm{~cm}\)
\[\mathrm{u}=-100 \mathrm{~cm}
\] \(\displaystyle \mathrm{v}=-100 \mathrm{~cm}\)
\[\frac{1}{v}+\frac{1}{u}=\frac{1}{f}
\] \(\displaystyle \frac{1}{100}-\frac{1}{100}==\frac{1}{f}\)
\[\frac{-2}{100}=\frac{1}{f}
\] \(\displaystyle \mathrm{f}=-50 \mathrm{~cm}\) Alternate answer for (i) Since u = v Therefore, object is placed at centre of curvature (C)
\[\mathrm{f}=\frac{R}{2}
\]
\[\begin{aligned}
& \mathrm{f}=\frac{-100}{2} \\
& \mathrm{f}=-50 \mathrm{~cm}
\end{aligned}
\]
(ii) \(\displaystyle \mathrm{m}=\frac{-v}{u}=\frac{-(-100)}{100}=-1\)
All Light - Reflection and Refraction questions2023 question paperNCERT solutions: Light - Reflection and RefractionPractice Light - Reflection and Refraction →
More from Light - Reflection and Refraction
- With the help of above given ray diagram, calculate the angle of refraction. Given that the refractive index of Medium 2 with respect to Medium 1 is…2026
- A student wants to obtain an erect image of an object using a concave mirror of 10 cm focal length. What will be the distance of the object from…2023
- An object is kept at a distance of 1m from a lens of power+2D: (i) Identify the type of lens. (ii) Calculate its focal length and distance of the…2023
- If the absolute refractive indices of two media X and Y are 6/5 and 4/3 respectively, then the refractive index of Y with respect to X will be:2025
- A student wants to project the image of a candle flame on a screen 60 cm in front of a mirror by keeping the candle at a distance of 15 cm from its…2023
- An object is placed in front of a concave mirror of focal length 12 cm. If distance of the object from the pole of the mirror is 8 cm, then use…2024
- (i) "In refraction of light through a rectangular glass slab, the emergent ray is always parallel to the direction of the incident ray." Why? Explain…2025
- The above ray diagram is to show image formation by a reflecting telescope. Reflecting telescope revolutionized our way of looking into the sky.…2026
CBSE Class 10 Science past-paper question from the 2023 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.