The energy of a photon is $3 \times 10^{-12} \ erg$. What is its wavelength in $nm$? $(h = 6.62 \times 10^{-27} \ erg \cdot s; \ c = 3 \times 10^{10} \ cm/s)$

If $\lambda_0$ and $\lambda$ are the threshold wavelength and the wavelength of incident light,respectively,the velocity of the photoelectron ejected from the metal surface is:

$A$ bulb emits monochromatic yellow light of the wavelength $0.57 \ \mu m$. If the rate of emission of quanta per second of the bulb is $14.33 \times 10^{19}$, the power of the bulb (in $Watt$) is $.....$

The shortest wavelength of $H$ atom in the Lyman series is $\lambda_{1}$. The longest wavelength in the Balmer series of $He^{+}$ is:

Newtonian mechanics is applicable to which objects and not applicable to which objects?

Calculate the radius of the fourth orbit of the $B^{4+}$ ion. (in $pm$)