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CBSE
Physics
Ray optics
A disc is placed on the surface of a pond which has a refractive index $\dfrac{5}{3}$ ​. A source of light is placed $4\,m$ below the surface of a liquid. Find the minimum radius of a disc so that light does not come out from a disc?
CBSE
Physics
Ray optics
The bouncing of a beam of light from a polished surface in some other direction is called -
A. refraction
B. reflection
C. dispersion
D. scattering
CBSE
Physics
Ray optics
Total internal reflection of light is possible when light enters from..............?

CBSE
Physics
Ray optics
Why is a diffraction grating better than a prism?

CBSE
Physics
Ray optics

Define absolute refractive index of a medium.

CBSE
Physics
Ray optics
What is the least radius through which an optical fiber of core diameter $0.05mm$ may be bent (as shown in figure) without serious loss of light? The refractive index of the core is $1.6$ and that of cladding is $1.5$
(A) $0.28mm$
(B) $0.78mm$
(C) $0.58mm$
(D) $1mm$

CBSE
Physics
Ray optics
What happens to the angle of refraction as the angle of incidence increases?
CBSE
Physics
Ray optics
A convex lens is in contact with a concave lens. The magnitude of the ratio of their focal lengths is $\dfrac{2}{3}$. Their equivalent focal length is 30 cm. What are their individual focal lengths?
A. -15, 10
B.  10,-15
C.   75, 50
D. -75, 50
CBSE
Physics
Ray optics
The Sun subtends an angle of half a degree at the pole of a concave mirror which has a radius of curvature of $15{\text{ }}m$. Then the size (diameter) of the image of the Sun formed by the concave mirror is.
A. $7.5{\text{ }}cm$
B. $6.55{\text{ }}cm$
C. $3.7{\text{ }}cm$
D. $13.1{\text{ }}cm$
CBSE
Physics
Ray optics
Define refractive index. You are given kerosene, turpentine and water. In which of these does the light travel faster? Which of these liquids are optically denser? Find out the speed of light in turpentine if the light travels from air to the turpentine.
RI of water is 1.33, Kerosene 1.44, turpentine 1.47. Speed of light in air is $3 \times {10^8}m/s$ .

CBSE
Physics
Ray optics
Which of the following would you prefer to use while reading small letters found in the dictionary?
(A) A concave mirror
(B) A concave lens
(C) A convex mirror
(D) A convex lens
CBSE
Physics
Ray optics
What is the difference between physical optics and geometrical optics?
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