Alternating Current — Physics STD 12 Science — Question

What was the difficulty with the wave theory ? How was this difficulty explained using Maxwell's Electro-magnetic wave theory ?

What is the meaning of stopping potential in the context of photoelectric effect?

Explain how the width of depletion layer in a p-n junction diode changes when the junction is (i) forward biased (ii) reverse biased.

Balmer series was observed and analysed before the other series. Can you suggest a reason for such an order?

A long narrow horizontal slit is placed 1mm above a horizontal plane mirror. The interference between the light coming directly from the slit and that after reflection is seen on a screen 1.0m away from the slit. Find the fringe-width if the light used has a wavelength of 700nm.

Work function of aluminium is 4.2eV. If two photons, each of energy 2.5eV, are incident on its surface, will the emission of electrons take place? Justify your answer.

What is called point dipole?

A compound microscope forms an inverted image of an object. In which of the following cases it is kely to create difficulties?

1. Looking at small germs.
2. Looking at circular spots.
3. Looking at a vertical tube containing some water.

Write formula for Bohr's frequency.

Define wavefront of a travelling wave. Using Huygens principle, obtain the law of refraction at a plane interface when light passes from a denser to rarer medium.