Curie temperature is the temperature above which

The angle between the lines whose direction cosines satisfy the equations $l + m + n = 0$ and $l^2 = m^2 + n^2$ is

The required amount of $KBr$ (molar mass $= 119 \, g/mol$) in grams to start the precipitation of $AgBr$ in $500 \, mL$ solution of $0.05 \, M \, AgNO_3$ will be ($K_{sp}$ of $AgBr = 5 \times 10^{-13}$)

The work function of a metallic surface is $5.01 \ eV$. The photo-electrons are emitted when light of wavelength $2000 \ \mathring{A}$ falls on it. The potential difference applied to stop the fastest photo-electrons is ............. $volts$ $[h = 4.14 \times 10^{-15} \ eV \ s]$

Three concentric spherical shells have radii $a, b,$ and $c$ $(a < b < c)$ and have surface charge densities $\sigma, -\sigma,$ and $\sigma$ respectively. If the potentials on the surfaces of these shells are $V_A, V_B,$ and $V_C$ respectively,then for $c = a + b$,which of the following is true?