Friction — Physics STD 12 Science — Question

If a thin lens is dipped in water, does its focal length change?

In the circuit symbol of a semiconductor diode, the arrow is pointing towards whom?

Light from a point source falls on a screen. If the separation between the source and the screen is increased by 1%, the illuminance will decrease (nearly) by:

1. 0.5%
2. 1%
3. 2%
4. 4%

Write the formula of Coulomb's law in vacuum or air.

What is the force acting on a charge Q placed in an electric field E?

Define the term 'activity' of radionuclide. Write its SI unit.

Write any two examples of paramagnetic substances.

Define the term 'drift velocity' of charge carriers in a conductor and write its relationship with the current flowing through it.

Answer the following questions regarding earth’s magnetism:
If you made a map of magnetic field lines at Melbourne in Australia, would the lines seem to go into the ground or come out of the ground?

How are infrared waves produced?