A person has a minimum distance of distinct vision of 50 cm .The power of lenses required to read a book at a distance of 25 cm is
3 D
1 D
2D
5 D
Three blocks of masses $m_1=2 \mathrm{~kg}, m_2=3 \mathrm{~kg}$ and $m_3=5 \mathrm{~kg}$ are placed on a horizontal frictionless surface and a force of 30 N pulls the system as shown below.The value of tension $T$ will be

15 N
30 N
6 N
10 N
Which one of the following graphs represents the velocity-time $(v-t)$ graph of a small spherical body falling in a viscous liquid?




A ray of light travelling in air is incident on one face of a parallel glass slab of thickness $t$ and refractive index $\mu$ at an angle of incidence $i$ .Total time spent by the ray inside the slab is
$\frac{\mu^2 t}{c \sqrt{1-\mu^2 \sin i}}$
$\frac{\mu t}{c \sqrt{\mu^2-\sin ^2 i}}$
$\frac{\mu^2 t}{c \sqrt{\mu^2-\sin ^2 i}}$
$\frac{t}{c \sqrt{\mu^2-\sin ^2 i}}$
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