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Physics Fill in the blanks.

Ray Optics and Optical Instruments · Gujarat Board (GSEB) STD 12 Science (GSEB - English Medium). 12 questions.

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12 questions · self-marked practice — reveal the answer and mark yourself.

Question 11 Mark
The radius of curvature of a concave mirror is $24 \ cm.$ The value of its focal length will be $...............cm$
Answer
$12 \ cm.$
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Question 21 Mark
The power of converging lenses is $...............$ and the power of divergent lens is $...............$
Answer
positive, negative
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Question 41 Mark
When lenses with focal length $+20 \ cm$ and $-30 \ cm$ are kept in contact, the power of the combination will be $...............$
Answer
$\frac{5}{3} \times D$
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Question 51 Mark
If the angle of incidence in an equilateral prism is $45^{\circ}$, then minimum deviation will be $...............$
Answer
$30^{\circ}$
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Question 61 Mark
When a lens made of a material of refractive index $1.5$ is placed in a liquid of refractive index $1.7,$ its focal length will $...............$
Answer
increase
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Question 71 Mark
Spherical aberrations in a lens is $...............$ if the total deviation over the both surfaces are uniformly distributed.
Answer
minimum
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Question 81 Mark
When a lens of refractive index $n$ is placed in a liquid of refractive index $n$, lens becomes $...............$
Answer
invisible
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Question 91 Mark
The phenomenon of total internal reflection is observed, while the angle of incidence is $...............$ than the critical angle.
Answer
more
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Question 101 Mark
If the critical angle of the medium is $60^{\circ}$ then the refractive index of the medium will be $...............$
Answer
$n=\left(\frac{1}{\sin c}=\frac{1}{\sin 60^{\circ}}\right.$$\left.=\frac{1}{\sqrt{3} / 2}\right)=\frac{2}{\sqrt{3}}$
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Question 111 Mark
When light entering from air to glass, for $...............$ colour of light critical angle will be minimum.
Answer
violet
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