An equiconvex lens made of glass of refractive index $$\frac{3}{2}$$ has focal length $$f$$ in air. It is completely immersed in water of refractive index $$\frac{4}{3}$$. The percentage change in the focal length is
A point object is moving at a constant speed of 1 ms$$^{-1}$$ along the principal axis of a convex lens of focal length 10 cm. The speed of the image is also 1 ms$$^{-1}$$, when the object is at ............. cm from the optical centre of the lens.
When light propagates through a given homogeneous medium, the velocities of
Total impedance of a series $$L$$-$$C$$-$$R$$ circuit varies with angular frequency of the $$\mathrm{AC}$$ source connected to it as shown in the graph. The quality factor $$Q$$ of the series $$L$$-$$C$$-$$R$$ circuit is