JEE Main 2006 — Modern Physics

A solid which is transparent to visible light and whose conductivity increases with temperature is formed by

If the ratio of the concentration of electrons that of holes in a semiconductor is $\frac{7}{5}$ and the ratio of currents is $\frac{7}{4}$, then what is the ratio of their drift velocities?

In the following, which one of the diodes is reverse biased?

The anode voltage of a photocell is kept fixed. The wavelength $\lambda$ of the light falling on the cathode is gradually changed. The plate current $\mathrm{I}$ of the photocell varies as follows :

If the lattice constant of this semiconductor is decreased, then which of the following is correct? 

An alpha nucleus of energy $\frac{1}{2} m v^2$ bombards a heavy nuclear target of charge Ze. Then the distance of closest approach for the alpha nucleus will be proportional to

The time by a photoelectron to come out after the photon strikes is approximately

The threshold frequency for a metallic surface corresponds to an energy of $6.2 \mathrm{eV}$, and the stopping potential for a radiation incident on this surface $5 \mathrm{~V}$. The incident radiation lies in

When ${ }_3 \mathrm{Li}^{\prime}$ nuclei are bombarded by protons, and the resultant nuclei are ${ }_4 \mathrm{Be}^8$, the emitted particles will be

The circuit has two oppositely connect ideal diodes in parallel. What is the current following in the circuit? 

If the binding energy per nucleon in ${ }_3^7 \mathrm{Li}$ and ${ }_2^4 \mathrm{He}$ nuclei are $5.60 \mathrm{MeV}$ and $7.06 \mathrm{MeV}$ respectively, then in the reaction $\mathrm{p}+{ }_3^7 \mathrm{Li} \rightarrow 2{ }_2^4 \mathrm{He}$ energy of proton must be