In an $AC$ generator,a coil with $N$ turns,all of the same area $A$ and total resistance $R$,rotates with frequency $\omega$ in a magnetic field $B$. The maximum value of $emf$ generated in the coil is

If $p \rightarrow (\sim p \vee \sim q)$ is false,then the truth values of $p$ and $q$ are respectively:

If $X = \{ 4^n - 3n - 1 : n \in N \}$ and $Y = \{ 9(n - 1) : n \in N \}$,then $X \cup Y$ is equal to

$1+\frac{1}{3 \cdot 2^2}+\frac{1}{5 \cdot 2^4}+\frac{1}{7 \cdot 2^6}+\ldots$ is equal to

The first line in the Lyman series has wavelength $\lambda$. The wavelength of the first line in the Balmer series is

In an experiment on photoelectric emission from a metallic surface,the wavelength of incident light is $2 \times 10^{-7} \ m$ and the stopping potential is $2.5 \ V$. The threshold frequency of the metal (in $Hz$) is approximately (charge of electron $e = 1.6 \times 10^{-19} \ C$,Planck's constant $h = 6.6 \times 10^{-34} \ J \cdot s$):