Light

1. A concave mirror of radius of curvature 1 m is placed at the bottom of a water tank. The mirror
forms an image of the sun when it is directly overhead. If the depth of water in the tank is 80 cm,
then the distance of the image formed is ________. (refractive index of water is 1.33)
(IJSO/Stage I/2017)
(A) 50 cm above mirror (B) On surface of water
(C) 110 cm above mirror (D) Image cannot be formed

2. As shown in adjacent figure, two plane mirrors M 1 and M2 are inclined to

each other at an angle 70° (angle M1OM2). Incident ray AB makes an angle
of incidence  on M1. This ray after reflection at B on M 1 and further at
C on M2 travels along the direction CD, such that path CD is parallel to
M1. Then angle  is ________.
(IJSO/Stage I/2017)
(A) 45° (B) 50° (C) 55° (D) 60°

3. For the same angle of incidence, the angle of refraction in three different media A, B, C are 15°,
25° and 35° respectively. Then which statement is correct? (A is refractive index of A)
(IJSO/Stage I/2017)
(A) A is maximum and velocity of light is minimum in medium A
(B) A is minimum and velocity of light is maximum in medium A
(C) A is maximum and velocity of light is maximum in medium A
(D) A is minimum and velocity of light is minimum in medium A

4. The ability of eye to focus both near and distant objects, by adjusting its focal length, is called
(IJSO/Stage I/2017)
(A) Myopia (B) Presbyopia (C) Accommodation of eye (D) Tyndall effect

5. Two plane mirrors M1 & M2 have their reflecting faces inclined at . Mirror M1 receives a ray AB,
reflects it at B and sends it as BC. It is now reflected by mirror M2 along CD, as shown in the figure.
Total angular deviation  suffered by the incident ray AB is (IJSO/Stage I/2018)

(A)  = 90° + 2
(B)  = 180° + 2
(C)  = 270° – 2
(D)  = 360° – 2

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6. In the adjacent figure, line AB is parallel to screen S. A linear obstacle PQ between the two is also
parallel to both. AB, PQ and screen S are coplanar. A point source is carried from A to B, along the
line AB. What will happen to the size of the shadow of PQ (cast due to the point source) on the
screen S? (IJSO/Stage I/2018)

(A) It will first increase and then decrease

(B) It will first decrease and then increase
(C) It will be of the same size for any position of the point source on the line AB
(D) Umbra will increase and penumbra will decrease till central position

7. Image is obtained on a screen by keeping an object at 25 cm and at 40 cm in front of a concave

mirror. Image in the former case is four times bigger than in the latter. Focal length of the mirror
must be ______. (IJSO/Stage I/2018)
(A) 12 cm (B) 20 cm (C) 24 cm (D) 36 cm

8. A glass cube of refractive index 1.5 and edge 1 cm has a tiny black spot at its center. A circular
dark sheet is to be kept symmetrically on the top surface so that the central sport is not visible
from the top. Minimum radius of the circular sheet should. (IJSO/Stage I/2018)
 1 1 1 
be  Given: = 0.707, = 0.577, = 0.447 
 2 3 5 
(A) 0.994 cm (B) 0.447 cm (C) 0.553 cm (D) 0.577 cm

9. Three objects of the same material coloured white, blue and black can withstand temperatures
up to 2000°C. All these are heated to 1500°C and viewed in dark. Which option is correct?
(IJSO/Stage I/2018)
(A) White object will appear brightest
(B) Blue object will appear brightest
(C) Black object will appear brightest
(D) Being at the same temperature, all will look equally bright

10. In a screw-nut assembly (shown below) the nut is held fixed in its position and the screw is
allowed to rotate inside it. A convex lens (L) of focal length 6.0 cm is fixed on the nut. An object
pin (P) is attached to the screw head. The image of the object is observed on a screen Y. When
the screw head is rotated through one rotation, the linear distance moved by the screw tip is 1.0
mm. The observations are made only when the image is obtained in the same orientation on the
screen. At a certain position of P, the image formed is three times magnified as that of the pin
height. Through how many turns should the screw head be rotated so that the image is two times
magnified?
(IJSO/Stage I/2019)

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 (A) 8 (B) 10 (C) 12 (D) 14

11. The triangular face of a crown glass prism ABC is isosceles. Length AB = length AC and the
rectangular face with edge AC is silvered. A ray of light it incident normally on rectangular face
with edge AB. It undergoes reflections at AC and AB internally and it emerges normally through
the rectangular base with edge BC. Then angle BAC of the prism is _________. (IJSO/Stage I/2019)
(A) 24° (B) 30° (C) 36° (D) 42°

12. The radius of curvature of a convex mirror is ‘x’. The distance of an object from focus of this mirror
is ‘y’. Then what is the distance of image from the focus? (IJSO/Stage I/2019)
y2 x2 x2 4y 2
(A) (B) (C) (D)
4x y 4y x

13. Two illuminated point objects O1 and O2 are placed at a distance 24 cm from each other along
the principal axis of a thin convex lens of focal length 9cm such that images of both the objects
are formed at the same position. Then the respective distances of the lens from O1 and O2 (in
cm ) are (IJSO/Stage I/2020)
(A) 12 and 12 (B) 18 and 6 (C) 14 and 10 (D) 16 and 8

14. A glass plate of uniform thickness t and refractive index  is as shown in the diagram. AB is the
incident ray and FG is the emergent ray. The angles of incidence and refraction are i and r
respectively. The perpendicular distance FC = x between the incident and the emergent rays is
called the lateral shift. Then (IJSO/Stage I/2021)

 cosisinr 
(A) x = t  sini − 
 cosr 
(B) x depends on refractive index 
(C) x is independent of the wavelength  of light
(D) Maximum value of x = t when i is close to 90°

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15. Two plane mirrors OA and OB are inclined at an angle  as shown in figure. A ray of light incident
parallel to BO strikes the mirror OA at point P. It gets reflected from mirror OA and then reflected
from the mirror OB, the ray finally emerges parallel to OA. The value of angle  is
(IJSO/Stage I/2022)

(A) 90° (B) 60° (C) 45° (D) 30°

16. Sir CV Raman announced the discovery of Raman Effect on February 28, 1928. He received 1930
Noble Prize in Physics for this discovery. Raman Effect is the discovery of (IJSO/Stage I/2022)
(A) Dispersion of light (B) Total Internal Reflection of light
(C) Refraction of light (D) Inelastic scattering of light

17. Focal length of a thin convex lens is 10 cm. An object is placed at a distance 15 cm in front of the
lens and a plane mirror is kept at 20 cm on the other side as shown in figure.
(IJSO/Stage I/2022)

(A) The final image is formed at distance 10 cm from lens towards the mirror
(B) The final image is formed at a distance 30 cm from lens means 10 cm behind the mirror
(C) The final image has magnification m=-2
(D) The final image has magnification m=+2

18. An object pin is placed at a distance 10 cm from first focus of a thin convex lens on its principal
axis, the lens forms a real and inverted image of this object pin at a distance 40 cm beyond the
second focus. The focal length of the lens is (IJSO/Stage I/2023)
(A) 16 cm (B) 20 cm (C) 25 cm (D) 40 cm

19. An ant is sitting on the principal axis of a convex mirror of focal length f, at a distance 2f from the
pole in front of the mirror. It starts moving on principal axis towards the mirror. During the course
of motion, the distance between the ant and its image (IJSO/Stage I/2023)
(A) throughout increases (B) throughout decreases
(C) first increases, then decreases (D) first decreases, then increases

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