Geometrical Optics — Physics STD 12 Science — Question

Which of the statements is true for p-type semiconductos.

1. Electrons are majority carriers and trivalent atoms are the dopants.
2. Electrons are minority carriers and pentavalent atoms are the dopants.
3. Holes are minority carriers and pentavalent atoms are the dopants.
4. Holes are majority carriers and trivalent atoms are the dopants.

How does the energy gap in a semiconductor vary, when doped with a pentavalent impurity?

Equal currents are flowing through two infinitely long parallel wires. What will be the magnetic field at a point midway when the currents are flowing in the same direction?

When a body is weighed on an ordinary balance we demand that the arm should be horizontal if the weights on the two pans are equal. Suppose equal weights are put on the two pans, the arm is kept at an angle with the horizontal and released. Is the torque of the two weights about the middle point (point of support) zero? Is the total torque zero? If so, why does the arm rotate and finally become horizontal?

Name the part of electromagnetic spectrum whose wavelength lies in the range of 10^–10 m. Give its one use.

The following table gives the wavelength range of some constituents of the electromagnetic spectrum.

S. No.	Wavelength Range
1.	1mm to 700nm
2.	400nm to 1nm
3.	1nm to 10-3nm
4.	< 10-3nm

Select the wavelength range and name the electromagnetic waves that are:

1. Widely used in the remote switches of household electronic devices.
2. Produced in nuclear reactions.

Which physical quantity has the unit Wb/m² ? Is it a scalar or a vector quantity?

Can X-rays be polarized?

What is Electrodynamics?