The radii of curvature of the faces of a double convex lens are 10 cm and 20 cm. The refractive index of the glass is 1.5. What is the power of this lens?

The time period of a simple pendulum made by using a thin copper wire of length L is T. Suppose the temperature of the room in which this simple pendulum is placed increases by 30$$^\circ$$C. What will be the effect on the time period of the pendulum?

Which one of the following physical quantities has the same unit as that of pressure?

Which one of the following statements is correct with regard to the material of electrical insulators?