Ray Optics and Optical Instruments — Physics STD 12 Science — Question

Two converging lenses of unequal focal lengths can be used to reduce the aperture of a parallel beam of light without losing the energy of the light. This increases the intensity. Describe how the converging lenses should be placed to do this.

The magnifying power of a simple microscope will be maximum for which colour of light and minimum for which colour of light?

The charging current for a capacitor is 0.25 A. What is the displacement current across its plates?

The length of the string of a simple pendulum is measured with a metre scale to be 90.0cm. The radius of the bob plus the length of the hook is calculated to be 2.13cm using measurements with a slide callipers. What is the effective length of the pendulum? (The effective length is defined as the distance between the point of suspension and the centre of the bob.)

Write the relation between threshold frequency and work function.

Does a conductor become charged when a current is passed through it?

Figure shows three point charges, + 2q, – q and + 3q. Two charges + 2q and – q are enclosed within a surface ‘S’. What is the electric flux due to this configuration through the surface ‘S’?

In photoelectric effect, what will be effect on velocity of emitted electrons, if the wavelength of the incident light is reduced?

The permeability of a magnetic material is 0.9983. Name the type of magnetic materials it represents.