When a semiconductor is doped with a donor impurity

An electromagnetic wave moves in vacuum. Its speed is c. Choose the correct options about the characteristics of electromagnetic waves:
(A) \( c = \frac{1}{\sqrt{\mu_0 \epsilon_0}} \)
(B) Electromagnetic waves are transverse in nature.
(C) Both the electric field and magnetic field vibrate perpendicular to the direction of propagation of waves
(D) Electromagnetic waves are longitudinal in nature.
Choose the correct answer from the options given below:

A transmitting antenna at the top of a tower has a height 32 m and the height of the receiving antenna is 50 m. What is the maximum distance between them for satisfactory communication in LOS mode? Given radius of earth \(= 6.4 \times 10^6\) m.

The resistivity of a material depends on

A pure inductor of 70 mH is connected to a source of 220 V. The frequency of the source is 50 Hz. The current in the circuit is:

A battery of 200 V charges a capacitor to \( 10 \times 10^{-6} \, C \). Now the battery is disconnected, and the plate separation is doubled. The potential of the capacitor will be

In a photoelectric experiment, the wavelength of incident light is increased from \( 5 \times 10^{-10} \text{ m} \) to \( 9 \times 10^{-10} \text{ m} \), while the intensity of radiation remains the same. Choose the correct statement from the following.

If \(A =\left(\begin{array}{cc}-a & b \\ c & a\end{array}\right)\) and \(A ^2= I\), where \(I\) is an Identity matrix of order 2, then which of the following is correct?

The order of basic strength of amines in aqueous solution is :

Elements of group-15, 16 and 17 form compounds with hydrogen with general formula MH3, H2M and HX (called hydrogen halides). Stability of these hydrides, along with M-H bond strength and basic nature decreases down the group. Boiling point of these hydrides mainly depends on the strength of their inter molecular forces.
Which of the following is liquid at \(20^{\circ} C\) ?
A. HCl
B. HI
C. HF
D. NH3
E. HBr
Choose the correct answer from the options given below:

The work function for a metallic surface is 4.0 eV. The longest wavelength of light that can cause photoelectron emission is approximately:

The mean of the numbers obtained on throwing a die having 1 on three faces, 2 on two faces and 5 on one face is:

Read the passage carefully and answer
The crystal field theory (CFT) is an electrostatic model which considers the metal-ligand bond to be ionic arising purely from electrostatic interactions between the metal ion and the ligand. Ligands are treated as point charges in case of anions or dipoles in case of neutral molecules. The five d orbitals in an isolated gaseous metal atom/ion have same energy, i.e., they are degenerate. This degeneracy is maintained if a spherically symmetrical field of negative charges surrounds the metal atom/ion. However, when this negative field is due to ligands (either anions or the negative ends of dipolar molecules like NH3 and H2O) in a complex, it becomes asymmetrical and the degeneracy of the dorbitals is lifted. It results in splitting of the d orbitals. The pattern of splitting depends upon the nature of the crystal field.
The colour of coordination compounds is attributed to