The thickness at the centre of a plane convex lens is 3 mm and the diameter is 6 cm. If the speed of light in the material of the lens is 2 $$\times$$ 10⁸ ms^$$-$$1. The focal length of the lens is ____________.

A Carnot's engine working between 400 K and 800 K has a work output of 1200 J per cycle. The amount of heat energy supplied to the engine from the source in each cycle is :

For what value of displacement the kinetic energy and potential energy of a simple harmonic oscillation become equal ?

An AC current is given by I = I₁ sin$$\omega$$t + I₂ cos$$\omega$$t. A hot wire ammeter will give a reading :